i made a post in a smaller forum and a moderator helped me a lot. he send me his ps file of this same tutorial and i played around with it. i figured out that when i use his postcard layer and merge it with a textlayer and then render it, the render comes out fine.
the problem is my postcard. i also tried rendering the same layer 3 times, but nothing would change. again, when i use his postcard layer everything works as intended.
i recently bought a new PC just to learn 3D related work and its very frustating to be stuck like this at the beginning.