Basically Germany stared losing way to many people, especially important people and leaders so due to that they had no other choice then to surrender.

They were both friends and enemies and the reason for this was because Germany was a greater world threat so even thought they didn't like each other they worked together and had sort of a mutual agreement.

The Manhattan project was a program that was in the U.S started by the U.S army that produced the first nuclear weapons.

They surrendered because they really didn't have any other choice, they were already losing to many people and they didn't surrender they would've continued to lose more.

This first bomb on Hiroshima was to scare japan into surrendering, the other reason for that particular area was because there were many factories in the area.

Nagasaki was not the first choice to bomb, they were going to bomb Kokura. Even though this wasn't their first choice, Nagasaki had weapon production in that area including torpedoes.