Hi NoBreezeNoFun
It seems like a few important aspects weren't covered well during your lessons.
This video should help you understand how to setup your kite correctly and the consequences of under-inflation:
This one should help you understand how your trimming system works and when/how to adjust it according to the conditions:
But yes, Basically you need to 1) Pump your kite Harder and 2) Only trim in light wind IF your kite backstalls, if it doesn't back stall then you don't need to trim it, simple! If you don't understand what backstalling is then you need to watch the video

Christian