Just got to the end of Duolingo, what now?

For context, I graduated from highschool this year with German as one of my subjects, reaching a level of B2 for speaking and writing and C1 for reading and listening. To try to maintain my knowledge I booted up Duolingo and within a few months I got to the end, which makes sense since it's just B1 level. However, I don't feel like doing the daily challenge or getting a perfect on every lesson is going to help me much. So what should I do now? I'd love to improve my grammar and vocabulary but besides studying the theory and learning the 3674 words Duolingo offers I'm lost. I listen to German media every so often but I just want something to reliably expand my knowledge and ideally get up to C1 across the board. Any advice is appreciated!