Spend time looking for absolutely well curated, well reviewed learning texts regarding a topic that interests you, often in the form of a university course or a blog on a specific topic. Then dedicate time every day to go through it, really be present, make notes and finish. Try learning approaches like spaced repetition learning.

If you want to solidify your knowledge, make a 30-min talk for your peers about the topic. Commit to make it perfect and be prepared for their questions.

And remember that friendship must be actively maintained.