would / would have

"If I found a wallet in the street" is a conditional clause.
We use past tense in a conditional clause to talk about things which are not true in the present and highly unlikely to be true in the future and use "would" + "base verb" in the main clause.

Personally I would not agree that it is highly unlikely for anyone to find a wallet in the street in the future.

因為事情發生了，並完成;而第二句,因為你將會做,好快就會做