Hi I made I mistake and I’ve purchased 100 keys that it’s equal to 22€ and I would like to ask for a refund. How can I do it?
I don’t think it’s possible, but you can ask the devs directly via messenger under
https://www.facebook.com/worldofairports/
or a DM on
https://instagram.com/worldofairports
Did you want to buy more to support the devs? 
It’s not funny.
Personally not sure if you can do anything about that, sort of a grey area (for example) what if I made the purchase and was not pleased with the purchase so I want my money back?? Should money get refunded for somethen I chose but didn’t want… (not saying this is your case) but it’s hard to tell