Quote Originally Posted by Danila
"В классе висит расписание". I think this would be correct?
This one is correct.

Quote Originally Posted by Danila
I haven't been to Moscow yet. But I know, that Moscow is a big city.
So if I write it with a comma, does it work?
Like:
Я ещё не был в Москве, но я знаю, что Москва - большой город.
This Russian translation is correct. But it doesn't matter whether you write it in one (with a comma) or two sentences.

Quote Originally Posted by Danila
And would it better to write:
У Москы есть Кремль, музеи, школы, библиотеки, ...
?
No, the correct version was mentioned above "В Москве есть Кремль, ..."