Visual Studio c# and php. I need support for an existing program.

I need to make some changes to existing code, in a program written by professionals who are no longer available. I have it in VS 2022, having upgraded from VS2017 and for example I can't get it to Build the installer. I can do some elementary stuff, but need my hand holding. It's a very niche product, see peoplesize.com. If you can do php on the website, so much the better. My web hosts moved a database on which everything depended, and now the knock-on effects are gathering pace.

Ideally, it would be a long term relationship, but intermittent.