"He gave me a bottle of milk."
Translation:Mně dal láhev mléka.
dával is repeated or describing the process of giving
mně is the right form for dative
"Mně dal láhev mléka." - wrong word order, Correct answer: "Dal mně láhev mléka." or "Dal mi láhev mléka." - I am a native speaker.
Those are among the accepted translations. (Most of the course contributors are native speakers.)