Thank you for the link.
So I should:
1. Create a fork.
2. from dev branch of fork I should create my branch russian-translation-update1
3. do local changes on files.
4. commit changes to my branch russian-translation-update1
5. then it's not clear:
a. should I send poll request to merge my russian-translation-update1 into dev branch of fork?
then do merge.
delete branch russian-translation-update1.
submit new poll request to merge dev branch of my fork with dev branch of original project?
or
b. create new poll request to merge my russian-translation-update1 directly into dev branch of original project ( colobot-data)?
So I should:
1. Create a fork.
2. from dev branch of fork I should create my branch russian-translation-update1
3. do local changes on files.
4. commit changes to my branch russian-translation-update1
5. then it's not clear:
a. should I send poll request to merge my russian-translation-update1 into dev branch of fork?
then do merge.
delete branch russian-translation-update1.
submit new poll request to merge dev branch of my fork with dev branch of original project?
or
b. create new poll request to merge my russian-translation-update1 directly into dev branch of original project ( colobot-data)?