Thank you for the comments. I believe the perspective is a bit distorted due to the area o chose to work in.
I the tutorial, Marc first makes the grid and then later chooses the area to work in. I probably should have chosen a smaller area to avoid distortions mainly on the right side of the picture.
I photobashed a picture for the sky and later on played around with it. I thought that it looked ok-ish but i see your point. It feels like the sky and clouds don't mesh together as well as they should.
As for the grass, the idea was to have near human height to give the impression of a natural wall/path leading to the gate.
To be honest, it's the part i hate the most, but nothing of what i tried worked the way i wanted, so i simply tried to finish it so i can post it and ask for tips and help.