nnoremap ; : to go to command mode.
Is there oposite shortcut that i can add to my .vimrc so that i won't press ESC every time to go back to normal mode?
Aborting command-line mode shouldn't be so frequent, why do you worry about having to press Esc?!
Some people remap Caps Lock to either Esc or Ctrl (outside of Vim), this also helps with leaving insert mode. Did you know that you can also use Ctrl-C to abort the command-line? Alternatively, you can define a mapping, e.g.
Choose some easy-to-type key sequence that you aren't likely to use in any text and map it to <Esc>. The sequence
If you ever have a need to enter that sequence into some file, just precede it with Ctrl-V.