Hi and welcome to the forum.
Nice introduction by the way.
Usually the reason that the screws do not turn is that they are corroded into the switch. The worst thing you can do is get the wrong size, cheap screwdriver onto it to try and remove it. I would suggest that you apply some plusgas and leave for a while. Then, using the correct size driver, of a good quality, try and remove the offending screw. If this fails then I would give the screw another squirt of plusgas and attempt to remove the screw with an impact driver. If that fails I would drill off the screw head and with the switch gear removed, apply even more plusgas using a set of mole grips on the remaining screw to twist it out. If this doesn't work then it may be a case of buying another switch.