I'd suggest listening to audiobooks of simple children books instead of shows/podcasts that might be too complex for you now. Also get a German-German dictionary and use it to read simple news websites (reading the definition of a word you don't know in German will help more than translating all the time), listen to radio news as normally the hosts will speak with a more clear intonation and you can pick up words instead of a stream of sounds.

That's at least what is helping me with Swedish.

Realistically if you want to get to at least a B2 level you are going to need much more than 15-30 min daily, even more because you aren't immersed in the culture and German is, frankly speaking, a quite hard language to learn. Sentence structure looks quite foreign if you only know English, grammar is complex, you have 3 different genders, etc.

Not trying to discourage you, much the opposite, go harder and you can do it but be realistic about it.