First thing is, do not believe anyone who's telling you that you can understand general relativity or quantum mechanics without understanding the math behind. If you have basic calculus knowledge I can recommend either looking at this book by Penrose which covers all the math and physics topics briefly or watch some of the physics courses online from Stanford. These courses are really enjoyable. They're not regular undergrad courses, but specially for people who have interest in the physics but doesn't have too much time to invest (for general relativity you'll need around 5-6 years of study in university.
I would start with classical mechanics or quantum entanglements. If you start with general relativity, most probably you wouldn't understand what he's talking about.
There are more courses, just check Standford Uni playlists.
Kleeneness is next to Godelness.