i hate rgammer its so confusing

Yeah, firstly, it's grammar not grammer.

Once you get the basics, the rest just falls into place. Hang in there. It'll come.

If you really can't stand it. There is a modern grammar checker which will correct your work and explain why. It's not cheap though.

(You'll get a discount if you're referred from this site, but still expect to pay over $100 for a life-time version.)