Bosaa: I have already opened a support ticket but the support team only answers me with useless automatic messages.
There's a pandemic and a huge release. Sorry, there's going to be a wait. Still you shouldn't expect staff to help you on these forums. While there are mods, that's not their primary function. But you shouldn't post any personal information directly to the forum. Wait until a staff member has made contact with you, if that's your goal, or wait on your support ticket.
Being as you got this from a 3rd party though GOG isn't likely to be able to help you too much.
Bosaa: I have been talking for a while with Instant Gaming and they insist they what the exact time the key was redeemed.
That's their way of weasling out of a refund. If you can't provide the information (And GOG may or may not provide it for you) then they'll refuse the refund for you being "uncooperative."