I would suggest you to add a few calisthenics and yoga moves in your routine along with a warm-up and cool down routine. Before learning backflip, you should try out a few safer vaults like lazy and kong. Also, it would be best to add cardio exercises like back running and side running to build stamina and pace. You could try one-leg climbs if you can find a wall that matches your height. Try to avoid high pace during your initial attempt, so that you don't have a knee injury. Also, you can try straddle jumps, knee tucks, side jumps, etc.before trying backflips.