Can i learn to fix cars on my own without school?

So i have autism, a certificate of completion, and a possible dumb idea? I had several years of a bad time with public school so i would prefer not to go back.

Im not that smart so im unsure if this is a good idea, but can i learn to fix cars on my own perhaps? what would you advise? where should i start?

I dont really have any better ideas on what to do in my freetime.

If you have a questions for me leave a comment.