Thanks for the report, the “matched 5 cards” is wrong and I’ll fix this in the next update. If you want to include learning cards in a filtered deck, you’ll need to use the new scheduler.
When selecting the custom study options two old tags, which have been deleted and the database manually updated, are pre-selected and I cannot remove the filter. Screenshot two shows the correct number of available tags, which is one called “neuekarte”.
Decks remember the last tags you used with them, even if those tags are no longer part of the tag list. While this could be improved, I imagine you could work around it for now by selecting a different tag and creating a new custom study, which should cause AnkiMobile to discard the previously remembered tags.