I recently removed popcorn ceiling texture from this drywall in my basement (an environmental test company said there was no asbestos). Underneath were all kinds of problems to fix, but these circles are the worst - I can barely sand anything off the top. I’m not sure when this was done, but it was probably 20+ years ago.

Does anyone have advice about how deal with this? I would like to repair the drywall and paint the ceiling. I’m totally new to this and don’t have many people I can ask. Thanks for looking!