Usually it takes about one business day at most to receive an answer from support. However, complex issues can take a bit longer.
What is important to keep in mind though is that GOG support doesn't work 24/7. They only work on (Polish) business hours and they don't work on weekends.
Since today is Monday and you wrote 'a few days ago' as you said you probably just wrote before the weekend so it's pretty normal that you don't have a reply yet.
On top of that we just had a huge sale so they probably have lots of tickets to work through. Since tickets are prioritized and payment issues and similar have a higher priority it might take a little until they get to your ticket. I'd say, if you haven't received a reply by Wednesday afternoon, write again.
Concerning turning games on the shelf into gift tickets: They do that for bought games as long as you don't download anything (neither the game nor the extras) if you contact them soon after buying and realizing your error. They normally don't do that for stuff they gift to their customers, but after originally refusing some people they have
reversed their decision and do that now!
So anybody who was refused when asking should ask again.