kkmanager showed about 3k new cards, maybe because of this? Or I did not install them correctly
Don't know, I never converted 3000 new cards at once.
There can be an error inside that console window - maybe it'll say what's the problem is.
If there's no error and it keeps hanging, you can try to copy all the cards in a separate from the game folder - so they won't become broken - and kill the game. Relaunch it.
If the problem persists, you can remove all the cards and launch the game without them.
If there's no problem without cards, you can try adding them bit by bit.
If one card at a time converts alright - then maybe it really just takes a lot of time.
But also maybe there's a problem with a specific card - in that case, you'll have to fish for it.