Imported Deck doesn't show up in overview

I’ve imported a deck from a friend of mine, but it just won’t show up on the title screen. I’m fairly new to anki, so I don’t know what the cause of the problem could be. I have installed all add-ons he uses.
The decks show up when looking at the card management, but they have a different symbol on the tag.
This is what myfunctioning decks look like:

And this is what his decks look like:

If anybody knows how to fix this problem I’d be very thankful :smiling_face_with_three_hearts:

“Atemsystem” is not a deck (Stapel) but a tag (Schlagwort) that has been assigned to some notes (Notizen).
You can click on the tag to list all notes with that tag and see which deck they’re in. If you have done that in the second screenshot it looks like they’re in the children decks of the deck “1. Semester Ana“.


Ah ok thank you, so if I want to learn those cards I create a deck with each tag and copy those cards into the decks?

That would work but I wouldn’t recommend it.
Instead, you can suspend all cards in the deck and then unsuspend the ones you want to study. Every time you advance to a new topic you can unsuspend the next batch of cards. That way, you’ll only have to study one deck which not only shows you the relevant new cards but also all the older cards whenever it’s time to review them.