Hey @BeyazMajeste, thanks for reaching out to the community!
When you sign up for Spotify Premium and get the trial, you should receive an email confirmation with a receipt.
If you received the receipt, but you can't use the Premium features, make sure you don't have multiple Spotify accounts following these steps.
In case you only have one account, reinstalling Spotify should do the trick.
Let me know how it goes.
“Music acts like a magic key, to which the most tightly closed heart opens.”
― Maria Augusta von Trapp