Thank you for the answer!
While I've managed to partition the HDD as I want during the pre-installation
of Trisquel I still cannot write in Bulgarian. I've chosen English for both
the system and writhing. In the freshly installed OS I tried to add BG
language support. All I get is BG translation after restart. I've opted out
the IBus. In Region and Language section input devices/methods I have both
EN-US and BG (in that order) and in System the setting are as follows:
Your settings
Menus: BG
Input: EN-US,
BG
Format: BG
System settings
Menus: EN (US)
Input: EN-US
Format: BG
So during the installation I chose BG format. Maybe thats the problem.
However, I guess that the input languages are OK but for whatever reason I
cannot switch them. Is the possible and how to add input language applet in
the GNOME Panel (Flashback) in Trisquel 7 or not?