I created a gog account with facebook there is no more facebook integration so I changed my email address but it tells me that my email address does not exist please help me

You'd have to log in through facebook before you could change it to an email address... i think...

Best you can do is contact a blue.
Maybe they can help you.
Otherwise put in a ticket.

edit: Going incognito i see it points to this article

https://support.gog.com/hc/articles/6535799816605?product=gog

I do them. but how to say that I have changed the password and the email and it does not work it says to me "user not found" because they have removed api facebook but me how I did I pay in addition I reported the beug they don't care, I even pm ponczo_GOG he doesn't answer so I'm in deep shit...

You only started this thread yesterday. How long has it been since you opened a support ticket, and when did you message ponczo_?

Unfortunately, support is typically much slower than that. But if you contacted a staff member 3 working days ago, I would've expected a response by now. I don't know if GOG removed anything, since the button is still visible, just not functional. It's possible something changed on Facebook's end and it requires GOG to update something.
There have been several threads about this issue. It's disappointing there hasn't been a single comment from staff to explain what's going on and when it'll be fixed.

Ok thank you, indeed I also find it strange that gog does not warn after I think that at the next update they will put the button ^^ on the other hand otherwise I ask for an account transfer