Sometimes when I shift it doesn’t go into gear all the way and jumps out of gear, why?

Normally you can shift forward from Neutral into High easy and falls into gear. When you try to shift into Low or Reverse it doesn’t lock in. The gears won’t line up unless you tap the throttle pedal to get the engine to rev up just above idle. Simply tap the pedal and release, this will allow the transmission shaft to slightly turn and line up the gear teeth and lock in the shift. Hold the shift knob, tap the throttle and you will feel the gear shift lock in, it will be a positive feel.