My code is not uploading to Arduino Uno, Please help! I am very new to arduino, so new that it is my first board. I keep running into this error 
avrdude: stk500_recv(): programmer is not responding 
avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x00

I have searched the internet for hours, tried solutions from almost every StackExchange question related to this topic, and even Reddit posts but none of those have been able to help me. All my settings are as they are supposed to be. Both the correct board and serial port are selected but it still keeps giving me this error: 
System wide configuration file is &quot;/home/rahat/Desktop/Arduino/arduino-1.8.13/hardware/tools/avr/etc/avrdude.conf&quot;
User configuration file is &quot;/home/rahat/.avrduderc&quot; 
User configuration file does not exist or is not a regular file, skipping
   ` Using Port                    : /dev/ttyS4
     Using Programmer              : arduino
     Overriding Baud Rate          : 115200`

 avrdude: stk500_recv(): programmer is not responding  avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00 
Also my operating system is Ubuntu 20.04 LTS
First of all find out on which port the Arduino is connected by running the command : dmesg | grep tty. You should get [82893.921017] usb 1-1: cp210x converter now attached to ttyXXX with the ttyXXX COM port.
Then check if the port is visible Tools-&gt;Port. If the port is not visible then you have a permission issue.