I have tested all answers of [this link](https://askubuntu.com/questions/41605/trouble-downloading-packages-list-due-to-a-hash-sum-mismatch-error). Unfortunately, none of them solved my problem. 

When I fire `apt update` up, it gives me: 

```
Hit:1 http://ir.archive.ubuntu.com/ubuntu bionic InRelease
Get:2 http://ir.archive.ubuntu.com/ubuntu bionic-security InRelease [88.7 kB]
Get:3 http://ir.archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]
Get:4 http://ir.archive.ubuntu.com/ubuntu bionic-proposed InRelease [242 kB]                                                           
Hit:5 http://ir.archive.ubuntu.com/ubuntu bionic-backports InRelease                                                                   
Get:6 http://ir.archive.ubuntu.com/ubuntu bionic/multiverse Sources [181 kB]                                                           
Get:7 http://ir.archive.ubuntu.com/ubuntu bionic/restricted Sources [5,324 B]                                                          
Get:8 http://ir.archive.ubuntu.com/ubuntu bionic/universe Sources [9,051 kB]                                                           
Get:9 http://ir.archive.ubuntu.com/ubuntu bionic/main Sources [829 kB]                                                                 
Get:10 http://ir.archive.ubuntu.com/ubuntu bionic-security/restricted Sources [4,548 B]                                                
Get:11 http://ir.archive.ubuntu.com/ubuntu bionic-security/universe Sources [167 kB]                                                   
Get:12 http://ir.archive.ubuntu.com/ubuntu bionic-security/multiverse Sources [3,180 B]                                                
Get:13 http://ir.archive.ubuntu.com/ubuntu bionic-security/main Sources [143 kB]                                                       
Get:14 http://ir.archive.ubuntu.com/ubuntu bionic-security/main i386 Packages [442 kB]                                                 
Get:15 http://ir.archive.ubuntu.com/ubuntu bionic-security/main amd64 Packages [651 kB]                                                
Get:16 http://ir.archive.ubuntu.com/ubuntu bionic-security/main Translation-en [211 kB]                                                
Get:17 http://ir.archive.ubuntu.com/ubuntu bionic-security/main amd64 DEP-11 Metadata [38.5 kB]                                        
Get:18 http://ir.archive.ubuntu.com/ubuntu bionic-security/main DEP-11 48x48 Icons [17.6 kB]                                           
Get:19 http://ir.archive.ubuntu.com/ubuntu bionic-security/main DEP-11 64x64 Icons [41.5 kB]                                           
Get:20 http://ir.archive.ubuntu.com/ubuntu bionic-security/restricted amd64 Packages [23.8 kB]                                         
Get:21 http://ir.archive.ubuntu.com/ubuntu bionic-security/restricted i386 Packages [4,280 B]                                          
Get:22 http://ir.archive.ubuntu.com/ubuntu bionic-security/restricted Translation-en [6,528 B]                                         
Get:23 http://ir.archive.ubuntu.com/ubuntu bionic-security/universe i386 Packages [617 kB]                                             
Get:24 http://ir.archive.ubuntu.com/ubuntu bionic-security/universe amd64 Packages [649 kB]                                            
Get:25 http://ir.archive.ubuntu.com/ubuntu bionic-security/universe Translation-en [218 kB]                                            
Get:26 http://ir.archive.ubuntu.com/ubuntu bionic-security/universe amd64 DEP-11 Metadata [42.1 kB]                                    
Get:27 http://ir.archive.ubuntu.com/ubuntu bionic-security/universe DEP-11 48x48 Icons [16.4 kB]                                       
Get:28 http://ir.archive.ubuntu.com/ubuntu bionic-security/universe DEP-11 64x64 Icons [111 kB]                                        
Get:29 http://ir.archive.ubuntu.com/ubuntu bionic-security/multiverse i386 Packages [4,292 B]                                          
Get:30 http://ir.archive.ubuntu.com/ubuntu bionic-security/multiverse amd64 Packages [6,760 B]                                         
Get:31 http://ir.archive.ubuntu.com/ubuntu bionic-security/multiverse Translation-en [2,700 B]                                         
Get:32 http://ir.archive.ubuntu.com/ubuntu bionic-security/multiverse amd64 DEP-11 Metadata [2,464 B]                                  
Get:32 http://ir.archive.ubuntu.com/ubuntu bionic-security/multiverse amd64 DEP-11 Metadata [2,464 B]                                  
Get:34 http://ir.archive.ubuntu.com/ubuntu bionic-security/multiverse DEP-11 48x48 Icons [29 B]                                        
Get:35 http://ir.archive.ubuntu.com/ubuntu bionic-security/multiverse DEP-11 64x64 Icons [2,638 B]                                     
Get:36 http://ir.archive.ubuntu.com/ubuntu bionic-updates/main Sources [311 kB]                                                        
Get:36 http://ir.archive.ubuntu.com/ubuntu bionic-updates/main Sources [311 kB]                                                        
Get:36 http://ir.archive.ubuntu.com/ubuntu bionic-updates/main Sources [311 kB]                                                        
Get:36 http://ir.archive.ubuntu.com/ubuntu bionic-updates/main Sources [311 kB]                                                        
Get:36 http://ir.archive.ubuntu.com/ubuntu bionic-updates/main Sources [311 kB]                                                        
Get:36 http://ir.archive.ubuntu.com/ubuntu bionic-updates/main Sources [311 kB]                                                        
Get:36 http://ir.archive.ubuntu.com/ubuntu bionic-updates/main Sources [311 kB]                                                        
Get:36 http://ir.archive.ubuntu.com/ubuntu bionic-updates/main Sources [311 kB]                                                        
Get:36 http://ir.archive.ubuntu.com/ubuntu bionic-updates/main Sources [311 kB]                                                        
Get:45 http://ir.archive.ubuntu.com/ubuntu bionic-updates/multiverse Sources [5,840 B]                                                 
Get:46 http://ir.archive.ubuntu.com/ubuntu bionic-updates/restricted Sources [6,536 B]                                                 
Get:47 http://ir.archive.ubuntu.com/ubuntu bionic-updates/universe Sources [278 kB]                                                    
Get:48 http://ir.archive.ubuntu.com/ubuntu bionic-updates/main i386 Packages [651 kB]                                                  
Err:48 http://ir.archive.ubuntu.com/ubuntu bionic-updates/main i386 Packages                                                           
  Hash Sum mismatch
  Hashes of expected file:
   - Filesize:650672 [weak]
   - SHA256:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
   - SHA1:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx [weak]
   - MD5Sum:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx [weak]
  Hashes of received file:
   - SHA256:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
   - SHA1:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx [weak]
   - MD5Sum:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx [weak]
   - Filesize:650672 [weak]
  Last modification reported: Sat, 07 Mar 2020 12:57:17 +0000
  Release file created at: Sat, 07 Mar 2020 14:34:50 +0000
Get:49 http://ir.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages [871 kB]                                                 
Err:49 http://ir.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages                                                          
Get:50 http://ir.archive.ubuntu.com/ubuntu bionic-updates/universe Translation-en [326 kB]                                             
Get:51 http://ir.archive.ubuntu.com/ubuntu bionic-updates/universe amd64 DEP-11 Metadata [264 kB]                                      
Get:52 http://ir.archive.ubuntu.com/ubuntu bionic-updates/universe DEP-11 48x48 Icons [193 kB]                                         
Get:53 http://ir.archive.ubuntu.com/ubuntu bionic-updates/universe DEP-11 64x64 Icons [438 kB]                                         
Get:54 http://ir.archive.ubuntu.com/ubuntu bionic-updates/multiverse amd64 Packages [10.1 kB]                                          
Get:55 http://ir.archive.ubuntu.com/ubuntu bionic-updates/multiverse i386 Packages [7,476 B]                                           
Get:56 http://ir.archive.ubuntu.com/ubuntu bionic-updates/multiverse Translation-en [4,636 B]                                          
Get:57 http://ir.archive.ubuntu.com/ubuntu bionic-updates/multiverse amd64 DEP-11 Metadata [2,468 B]                                   
Get:58 http://ir.archive.ubuntu.com/ubuntu bionic-updates/multiverse DEP-11 48x48 Icons [29 B]                                         
Get:59 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/multiverse Sources [1,796 B]                                                
Get:60 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/universe Sources [20.5 kB]                                                  
Get:61 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/main Sources [66.6 kB]                                                      
Get:62 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/restricted Sources [5,592 B]                                                
Get:63 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/main amd64 Packages [111 kB]                                                
Get:64 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/main i386 Packages [82.0 kB]                                                
Get:65 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/main Translation-en [39.0 kB]                                               
Get:66 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/main amd64 DEP-11 Metadata [3,580 B]                                        
Get:67 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/main DEP-11 48x48 Icons [29 B]                                              
Get:68 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/main DEP-11 64x64 Icons [5,301 B]                                           
Get:69 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/restricted i386 Packages [7,820 B]                                          
Get:70 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/restricted amd64 Packages [16.8 kB]                                         
Get:71 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/restricted Translation-en [5,732 B]                                         
Get:72 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/universe amd64 Packages [141 kB]                                            
Get:73 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/universe i386 Packages [134 kB]                                             
Get:74 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/universe Translation-en [27.6 kB]                                           
Get:75 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/universe amd64 DEP-11 Metadata [13.1 kB]                                    
Get:76 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/universe DEP-11 48x48 Icons [5,921 B]                                       
Get:77 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/universe DEP-11 64x64 Icons [16.2 kB]                                       
Get:78 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/multiverse i386 Packages [3,264 B]                                          
Get:79 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/multiverse amd64 Packages [7,588 B]                                         
Get:80 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/multiverse Translation-en [2,836 B]                                         
Get:81 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/multiverse amd64 DEP-11 Metadata [2,468 B]                                  
Get:82 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/multiverse DEP-11 48x48 Icons [29 B]                                        
Get:83 http://ir.archive.ubuntu.com/ubuntu bionic-proposed/multiverse DEP-11 64x64 Icons [2,638 B]                                     
Get:84 http://ir.archive.ubuntu.com/ubuntu bionic-backports/main Sources [2,532 B]                                                     
Get:85 http://ir.archive.ubuntu.com/ubuntu bionic-backports/universe Sources [2,496 B]                                                 
Fetched 18.0 MB in 1min 11s (253 kB/s)                                                                                                 
Reading package lists... Done
E: Failed to fetch http://ir.archive.ubuntu.com/ubuntu/dists/bionic-updates/main/binary-i386/by-hash/SHA256/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx  Hash Sum mismatch
   Hashes of expected file:
    - Filesize:650672 [weak]
    - SHA256:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
    - SHA1:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx [weak]
    - MD5Sum:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx [weak]
   Hashes of received file:
    - SHA256:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
    - SHA1:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx [weak]
    - MD5Sum:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx [weak]
    - Filesize:650672 [weak]
   Last modification reported: Sat, 07 Mar 2020 12:57:17 +0000
   Release file created at: Sat, 07 Mar 2020 14:34:50 +0000
E: Failed to fetch http://ir.archive.ubuntu.com/ubuntu/dists/bionic-updates/main/binary-amd64/by-hash/SHA256/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
E: Some index files failed to download. They have been ignored, or old ones used instead.

```

The `/etc/apt/sources.list`:

```
###### Ubuntu Main Repos
deb http://ir.archive.ubuntu.com/ubuntu/ bionic main restricted universe multiverse 
deb-src http://ir.archive.ubuntu.com/ubuntu/ bionic main restricted universe multiverse 

###### Ubuntu Update Repos
deb http://ir.archive.ubuntu.com/ubuntu/ bionic-security main restricted universe multiverse 
deb http://ir.archive.ubuntu.com/ubuntu/ bionic-updates main restricted universe multiverse 
deb http://ir.archive.ubuntu.com/ubuntu/ bionic-proposed main restricted universe multiverse 
deb http://ir.archive.ubuntu.com/ubuntu/ bionic-backports main restricted universe multiverse 
deb-src http://ir.archive.ubuntu.com/ubuntu/ bionic-security main restricted universe multiverse 
deb-src http://ir.archive.ubuntu.com/ubuntu/ bionic-updates main restricted universe multiverse 
deb-src http://ir.archive.ubuntu.com/ubuntu/ bionic-proposed main restricted universe multiverse 
deb-src http://ir.archive.ubuntu.com/ubuntu/ bionic-backports main restricted universe multiverse 

```

I don't know why exactly it is happening and what's the solution. 

Thanks in advance.