I'm having a really hard time getting trimming.
For example on climbing, I pull back on the joystick, increase powet to full. Then press the END key on the numeric keypad a couple of times. Let go of the stick but it doesn't stay in the climb, instead it drops back down. So I repeat the process and the same thing happens over and over again.
Unless your climbing out over an obstacle or otherwise trying to avoid something by climbing over it, don't use full throttle. Try, from straight and level flight, adding 100 to 200 rpms. This should give you a climb rate in the neighborhood of 300-600 fpm. Reducing power will allow yo to descend. Reducing power and adding some backpressure is used to slow down, maintain altitude, and get you into the flap extend arc (white arc of airspeed indicator). Give the lessons a try. They will make your flying experience much more fun and enjoyable.