I am playing on a Mac on Mac OS Catalina. I need free game suggestions that are easy to learn and run. they also cant be 18+.

Try Celeste and Geometry Dash

You can try do Speedruns of Flash games with Adobe Flash. I'm not familiar with Mac but it shouldn't be a problem trying that. I can suggest Fist Punch (i also did runs) from Cartoon Network website, there's the web and flash version.