They should be self-tapping screws. Better still are drill point. What are the threads like? If you are trying to use wood screws (coarse thread) then you will also struggle. You should have fine threaded screws for metal studs.
These are just standard bugle-head drywall screws. From comparing online images they look fine-threaded. I got a couple in apparently just by pressing really hard, but all the others just seem to skate off the stud and tear up the plasterboard.
Hanging the plastetboard horizontally? That was how I learned to work with sheetrock and metal stud walls. It gives you better leverage. The screws can skip around if there is any flex in the stud. Hanging it horizontally is supposed to help.
They should be self-tapping screws. Better still are drill point. What are the threads like? If you are trying to use wood screws (coarse thread) then you will also struggle. You should have fine threaded screws for metal studs.