I can't get on with keyboard and mouse. Is there any way to use a control / gamepad??

Well the only thing which comes to my mind might be adding the Game to steam... there you can craft your own gamepad controls if go in the steam overlay.

It is an old game so probably that's why it doesn't have gamepad support. You can also check this website to confirm if any games have controller support. https://pcgamingwiki.com/wiki/SWAT_4

Although I believe there are some programs that can make your controller work with such games but I have never tried it so you will have to search for it.