My 8 week old puppy wants to eat grass and chew on his leash when I take him out to potty, do you have any tips?

I would pick an area where the puppy has as little "stuff" to interact with as possible and interrupt the leash biting. Pick him up and move him to another spot and the moment he potties lots of praise, pick him up and carry him inside. It can take a bit for puppies to understand why they are being taken outside at first.

Have you watched the videos in the puppy courses you purchased?