I don't have a lot to say about 'Theaetetus'. The dialogue is (mostly) between Socrates and a young man named Theaetetus. Theaetetus is very smart and humble and Socrates treats him with respect and gentleness. The dialogue is concerned with how we know things.
The biggest thing that I learned was a bit of personal discovery. Discussions of epistemology make my eyes glaze over. This may be my problem with Kant, too. Not sure what it is but I think the problem is is that the theories of knowledge seem incomplete or unconvincing.
This doesn't bode well for the rest of the year, either. Both Locke and Hume have pieces concerning human understanding. They're followed up by part of Kant's 'Critique of Pure Reason'. August and September could be long . . .