yo let me help you out a little and recommend some resources. here are some series free on youtube: David Spivak and Brendan Fong did a lecture series on their book, Seven Sketches in Compositionality, you can find it on the "Topos Institute" youtube channel. "The Catsters" also have a great introductory series. as far as straight textbooks go, the only intro ones I recommend are 1) Awodey, 2) Riehl, and 3) Seven Sketches.
and one last general tip: categories are simultaneous generalizations of monoids and posets, so whenever you don't understand something, try working it out in the cases where there's only one object (= monoid) or when there's at most one arrow between a pair of objects (= poset)
and one last general tip: categories are simultaneous generalizations of monoids and posets, so whenever you don't understand something, try working it out in the cases where there's only one object (= monoid) or when there's at most one arrow between a pair of objects (= poset)