Is there a simple way to know when to use ś vs sz for the verb? Like in "You ARE......" it's "jesteś" but for "You LIKE...." it's "lubisz". Based on the jesteś I intuitively tried lubiś and got it wrong since it uses "sz". Is it because of the last letter in the verb before the suffix or is it more complicated?
mleko, not "mlecko"
This is one of the beginning lessons of Polish on Duolingo. In the beginning, Duolingo teaches all the direct translations of pronouns so that learners understand ty = you [singular] before learning how to conjugate verbs. In common speech, the ty is omitted because lubisz can only mean ty lubisz.