What is the prepositional phrase for donovan would rather have cookies before dinner

The prepositional phrase is before dinner
before could play as conjunction or preposition

when it's joining 2 sentences then it's a conjunction
if it's not and having an object after then it's a preposition

1one sharp difficulty presented itself. in the intervening twenty-five years my name had become reasonably well known.2 this being so, my trip demanded that i leave my name and my identity at home.3 i had to go alone and i had to be self-contained, a kind of casual turtle carrying his house on his back.4 with all this in mind i wrote to the head office of a great corporation which manufactures trucks.