My door check strap mechanism broke a while ago and finally got round to buying a new one. I've come to unscrewing the old one but cannot undo the screws as they are ridiculously tight managed to get one out about a millimetre but did not want to continue as the metal was starting to wear away on the actual screw. I've sprayed WD40 to try and help but am having problems

Above is the link of the door check strap just encase no one has any idea what I'm on about
ANY IDEAS OR HELP PLEASE!
Above is the link of the door check strap just encase no one has any idea what I'm on about