macOS Catalina

How do I uninstall catalina and go back to whatever i was using. I only use my macbook pro late 2013 model for internet and microsoft word. I dont need the update, my computer was working fine b4 i updated. it was on 2 OS b4 it and it worked flawlessly. Now just putting on a 5 min youtube video it overheats and kicks the fan on. I hate it, please help me switch it back.

Thank you