Conjugate “to be”

What’s the German verb for to be?

Let’s start conjugating with a little multiple choice :).
How do you say “I am.” in German?

Why is sein so awefully irregular (just like “to be”)? 

How do you say “you are” (singular) in German?

And how do you say “we are” in German?

Enough multiple choice… let’s step up our game.
Fit the persons with the right forms.

And now everyone’s favorite… typing!
Type in the right forms.