Woo! Congrats!

At least for me completing a course was a big occasion... which is to say, I shared it on all the (few) social media I could.

... I mean, there should have been "lessons" on tenses, articles and conjugations on Duolingo. What's going on?

The book also should have said that "sein" is conjugated differently for almost each pronoun, in the present and simple past. (Kind of like the English "to be", but even more.) So those weren't different verbs, but different forms.

"Wart" is for the familiar second person plural... I don't know how you're getting on with this concept. Well, if you recall at all, Spanish also has this, with "vosotros"... Although in many varieties that's going away.

Which, on a related note, I find pretty interesting, because German and Spanish are the only languages that preserve this form of address. English has all second person pronouns collapsed into "you", of course. French, Russian, Polish, Dutch... and Welsh only distinguish between the singular and the plural/polite.