How to install SDK packages offline after download is complete?
of course you can, use below link and Download Offline any package's you need :

http://downloads.puresoftware.org/files/android/


// i think your ip banned from Google.like IRAN Ip :) For Online packages download.

after Download :

Extract Folder, (Example : build-tools ) in : SDK Root Directory.
or if doesnt exist with this name, Create a folder with this name ( build-tools ) and then Open Sdk manager and now, you can see Added Package in List.

or you can Download Bundle : 
All Android Studio Packages
(Not Recommended)

and Attend please, this is your SDK Root Directory :

/home/mehran/Application/Android/android-sdk-linux/


Extract all of this packages in this Directory.

also, maybe usefull :

Adding SDK Packages