I have to write 4 sentences using an adverb and 4 using a preposition. Could you please check? I will list the adverbs first.

1.I'm sure he let the dog come in last night.
2.We watched the balloons floating far above our heads.
3.The bus drove past the people waiting at the bus stop.
4.Don't turn that log over so quickly!

1.The goats are in the far pasture.
2.You might have to wade across the creek to find the trail again.
3.Meet me outside the front door after you've finished shopping.
4.If the gate won't open, you'll have to climb over the fence.

I think they are right, although you haven't indicated which words are adverbs and which are prepositions.

1.in

2.above
3.past
4.over

1.in
2.across
3.outside
4.over

Two of your adverbs are actually prepositions.

The rest are correct.

Your sentences are correct! Here's a breakdown of the adverbs and prepositions used in each sentence:

Sentences using adverbs:
1. Last night - It describes when the action of letting the dog come in occurred.
2. Far - It describes the distance by which the balloons were floating above our heads.
3. Past - It describes the direction in which the bus drove regarding the people waiting at the bus stop.
4. Quickly - It describes the speed at which the log should not be turned over.

Sentences using prepositions:
1. In - It describes the location of the goats, indicating that they are inside the far pasture.
2. Across - It describes the action of moving from one side of the creek to the other in order to find the trail again.
3. Outside - It describes the location where the meeting should take place, namely outside the front door.
4. Over - It describes the action of climbing from one side of the fence to the other since the gate won't open.

Well done on using adverbs and prepositions effectively in your sentences!