ok first of all, you need to try out small things before you make complicated things. otherwise, you'll just get angry with yourself and quit. start small.
as for the tree thing (seriously, if you don't improve that english, don't ask for help in english), start with a demo - make a mod that detects you right-clicking the ground with a stick. when you detect that, spawn 2x EntityFallingBlock (i think it's called that). spawn them at x-1, y+4, z and x+1, y+4, z. let one have a blocks.log as it's block and the other should have blocks.leaves as its block. now give them a bit of vertical movement (i don't remember if you even have to, maybe not) using motionY and you're done with a demo. then, build on top of that.