How the hell does Mosfet work??

So I bought another Arcturus Tactical gun because the I accidentally broke and lost the part inside the gun (R.I.P first gun), but got a new one, on the other hand it was built different because I saw that the trigger is different and I was excited. So I was messing around with it and activated the trigger switch system, changing my full auto trigger into binary trigger. I tried changing it to full auto again but it stays on binary trigger. At other times I sometimes activate burst fire from semi auto. So yeah, I'm obviously doing something wrong, the gun is perfectly fine, just need to know how to change firing types.