OP... Many of us have spent a lot of years with horses. Some have had the benefit of professional instruction and some of us have learned mostly on our own. Read, watch, ask a lot of questions. And sometimes you end up in the dirt but that causes you to go seeking a solution. It's a process that never ends. Nobody has learned it all.
Copperhead's advice is good. Once the horse is reliable and has been for some time, then he will be ready for other riders.
Good luck to you.
If you ever find yourself in a fair fight, it's because your tactics suck. ~ Marine 1SGT J. Reifinger