Need help: cards are not displayed

I’ve been working with Anki for a while and it helped me a lot! But now I’m struggeling with a problem I cant seem to fix.

I’ve written maybe 500 cards in diffrent decks and they worked as usual, when i opened Anki today only one third of them are displayed in the category “new” or “due” next to the decks in the overview and I haven’t studied them yet! The weird thing is that I can see them in the “Cardmanagment”. I tried to create a “personalized study session” and to increase the amount of cards per day, but it didn’t change anything.

So I’m looking out for help, because my studiing really depends on those cards, thank you very much!!

PS.: excuse me if some translations are not correct, i hope my problem is understandable

When you have decks nested in a tree, the limits of the parent decks affect how many cards the child decks will show. You could increase the limits on both parent and child decks to have Anki show more cards, but please bear in mind that studying many new cards at once is not recommended: Anki's not showing me all my cards! - Frequently Asked Questions