Here are a few tips:
-to name a project in unity, go to edit > project settings > player > project name, you can change the company name too!
-don't put colliders for not important objects like grass, or the tombstone. It makes walking feels clunky and wrong
-you can handle the wasd system just by using Input.GetAxis("Horizontal") (for ad) and Input.GetAxis("Vertical") (for ws), althrough I prefer Input.GetAxisRaw. This will give you a number between -1 and 1 that will indicate the direction the player wants to move (for example, if the player presses a or the left arrow, it will give you -1, and that means left)
-when releasing a button, the zombie continues to move! That is because the zombie's rigidbody kept momentum from the last moves. To avoid this, try increasing the rigidbody's drag value, or better, use Vector2.SmoothDamp to gradually change the rigidbody's velocity. and there's too friction too
-great pause menu!
-try make an idle and jump animation, this will make your zombie a lot more alive ;) (and the same goes for every single object that you have in your game, try making it immersive!)
-I think you tried doing a portal or something like that but it is buggy. When you start at making games, try doing things simple, but good (that not means you shouldn't be original but try something at your scope)
-I think the music is handmade, maybe with Bosca Ceoil or something like that... It works fine, it's not repetitive at all. Nothing to say on that.