I'm currently in my 4th semester as a physics student. About a year back, I picked up a book titled Lectures on Differential Geometry (can't remember the author off the top of my head) and always wanted to dive in, but could never grasp any information. Today in my cosmology lecture, I was introduced to the field equations and tensors, and my professor brought up differential geometry.
I'm mainly looking for advice on resources/approaches to learn the subject, at least to begin understanding the concepts in differential geometry. I have taken Calc 1-3, DE & Linear Algebra, as well as currently taking a second course in Linear Algebra.
Sort of off topic, but I've also been interested in topology. Any advice there as well?