Since upgrading to Mojave on my mac, I can't find a way to make PS CS5 work.

CS6 and earlier programs HAVE NOT BEEN TESTED AND WILL NOT BE UPDATED for Mac El Capitan or newer operating systems

-which means that you try to use CS6 and earlier at YOUR risk of having problems due to Apple updates

-Apple did not maintain backward compatibility with old programs in El Capitan or newer operating systems

--Adobe has a workaround to Apple's problem of not maintaining backward compatibility

--READ HERE https://forums.adobe.com/thread/2301916 for an Adobe solution to installing old programs, including a link to installing the old Java runtime that is required

--Also read for more information https://forums.adobe.com/thread/2458382

--and https://helpx.adobe.com/x-productkb/global/install-or-run-applications-new.html