How long do you think till I have my back handspring?

In my opinion, it depends on how scared you are. Tell your coach to give you a heavy spot on a MAT not the floor and keep doing it on a mat until you only need a light spot then when you have it by yourself. After you have it on the mat, then tell your coach to lightly (or heavily if you want) spot you on the floor. If you have it by yourself on the trampoline already then you're doing pretty good! You could actually get it down by the end of next week since you're taking 3 classes(: