Slipping after I been riding for 20 mins and it heats up

Clutch pack is probably on its way to used up. You should find someone with right tools and expertise to replace it. You could also acquire the tools and knowledge to do it for yourself if you are willing to learn why the shops charge so much to do this job. A second possibility is that there is not enough freeplay (or maybe even no freeplay) in the clutch actuation mechanism and that is causing the slippage as the clutch pack heats up to (and probably beyond in your case) operating temperature. A simple adjustment might restore the clutch to normal operation but don’t expect it to last forever if such an adjustment “fixes” it. All the burnt lining contamination in the oil is not very good for the rest of the internal parts… stopping up oil filters and impeding oil supply is a big concern. Or maybe you have this problem… https://www.youtube.com/watch?v=D-KThaAZ...