That said, letter with diacritic vs separate letter is a surprisingly fraught topic, the same character can be considered a letter in one language and not a letter in another. Look up collation rules in European languages for a real nightmare...
Are you really telling us Slavs that we are wrong in what we (and our governments, educational systems and language authorities) consider a letter in our native languages and should stop saying our alphabets have however many letters we say they do for decades now because Germans happen to use different logic when counting their letters..?
I mean.. really?
I'm so astonished by that logic I don't even know what to tell you. Different languages can have different rules you know.
Edit: thanks for the downvote. How dare I tell a person who just claimed half of Europe is composing their alphabets wrong because Germans do it differently that they are short sighted.