From personal experience, I’ve found that it’s easier to make a new game that is roughly similar scale of your previous game, but add one extra element that you are not familiar with, and make the game focus on it.
Unfamiliar with physics? Make a game that only uses features you’ve used before, but also includes physics. This way, while making the game, you will be able to earn some new experience, experiment with new ideas, and possibly have fun.
I don’t really have much experience with Unity tutorials, so I can’t suggest anything specific.