You say: "If there were upon the earth Angels live in tranquility, We would have sent down to them from the heaven an Angel as a Messenger".
Angels are a peculiar creature created from the Light. They all are believers who don’t disobey the Lord in anything He Commands them; and they do whatever they are ordered. They are considered as the governing servants of the universe. They are also acting as the Messengers to convey the Message from the Lord to human Messengers. By testifying Adhikr, Jinns and mankind can reach higher in ranks before Lord than Angels as explained in verse 3: 79. Only by the remembrance of Allah with Adhikr, the hearts will achieve tranquility as explained in verse 13: 28.
By the second coming of Jesus, the Arabic Quran reading Fujjar who hide and reject Adhikr and accept Antichrist as their lord will be killed by the other people belonging to Messenger’s community. Then men and women on earth will be transformed into the characters of Angels and they will lead a life here peacefully and in tranquility without any sexual passions and diversities as explained in verse 4: 91. See explanation 4: 159; 9: 5 and 15: 7-8.