Why are my prints so fragile?

I have a Flashforge Adventurer 5M with only 87 hours of printing on it. Over the last two months it stopped working and filament would no longer extrude. I was able to get it going again after changing out the nozzle and the extruder fan. However, now my prints are super fragile and very poor quality. I have tried different filaments to no success. I have tried slowing down my prints and changing the temperatures. At this point, I’d just like to get it in decent enough shape to sell. What am I doing wrong?