I will be very grateful to you! If you own git, the best way is to send a pull request to my fork. Now I'll drop the links. If you don't know a git, you can just send edits in the form that you can do. Thanks!
Discussion
Repo: https://github.com/Perlover/tip-cards
Czech translation: https://github.com/Perlover/tip-cards/blob/perlover/improvements/frontend/src/locales/cs.json
There are plural forms in cs.json file. For Czech, this means that you will see three translated forms in one string, separated by " | ". The first option is for the numeral "1". The second option is for "2", "3" and "4". And the third part is for the remaining numbers.