How can I improve in chess?

Let me get straight to the point. I want to grow in chess. I used to play a lot 6-7 months ago, and at that time, my peak Elo was around 800+ (below average?). After watching Gukesh Dommaraju achieve the title at such a young age, it inspired me, and now I want to make a comeback. But I can’t seem to increase my Elo—I was stuck at that level before as well. Is there any free course out there where I can learn and improve? Also, is there any group chat for chess? If not, we could make one to keep our interest up. Thanks