Let me add a bit of slang in here too. To understand people you'd have to know the "street language" too, not just the polite way of saying things.
How much is it? - Mis see maksab?
I don't understand - Mida? Mis asja? (quite rude, but people use it)
I get it - okei
I don't know - Mul pole aimu ka!
ma'i tea.
Excuse me where is the toilet? - Kus on WC (veetsee)? Kus on peldik?
Essentials
Hello - Tere päevast / Tere / Tsau