When you see Lemma&#x2F;Proposition&#x2F;Theorem think of it as an API that you can interface with.<p>Skip the proofs on the first read (this is the implementation, and may or may not be enlightening.)<p>But, number one rule with learning maths is: you got to do it yourself. Play with it somehow. It&#x27;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.<p>Seriously, you absolutely cannot learn this stuff just by reading. Or, at best you may learn a very small fraction of it.<p>IMO, this text is far from &quot;typical definition-theorem-proof&quot;. There is plenty of other prose and examples there aswell.