I can't seem to unscrew them
None of the two screwdrivers that came with the fix kit seem to fit these screws.
The screws are single-use by Apple standards; they are easier to strip, and provide less torque feedback when trying to make them turn for the first time. For better results, they can be turned with a 2.0 flathead screw driver, or a 000 Phillips instead.
There should have been three screwdrivers in a replacement kit. The Phillip screwdriver will unscrew all the phillips heads in the iPhone. Maybe the angle at which you are trying to unscrew them from is incorrect. You need to position the screwdriver directly above the screw and not at an angle.