When you see Lemma/Proposition/Theorem think of it as an API that you can interface with.
Skip the proofs on the first read (this is the implementation, and may or may not be enlightening.)
But, number one rule with learning maths is: you got to do it yourself. Play with it somehow. It's similar to learning a new (or first) programming language (or API): have a project in mind and try to do it using that language.
Seriously, you absolutely cannot learn this stuff just by reading. Or, at best you may learn a very small fraction of it.
IMO, this text is far from "typical definition-theorem-proof". There is plenty of other prose and examples there aswell.
Skip the proofs on the first read (this is the implementation, and may or may not be enlightening.)
But, number one rule with learning maths is: you got to do it yourself. Play with it somehow. It's similar to learning a new (or first) programming language (or API): have a project in mind and try to do it using that language.
Seriously, you absolutely cannot learn this stuff just by reading. Or, at best you may learn a very small fraction of it.
IMO, this text is far from "typical definition-theorem-proof". There is plenty of other prose and examples there aswell.