In what year was the first gun invented and by whom?

Answer 1

(Fire lances", gunpowder-propelled arrows, were used in China from at least 1132 AD, after that they had there own firearms (made out of bamboo it looked like a canon)
The arquebus, from 1410, was one of the first firearms that were relatively light (they still required a stand to balance them) and could be operated by one person. One of these weapons was first recorded as being used in the Battle of Agincourt in 1415, although this was very much a medieval battle. The musket was originally a heavier form of the arquebus, which fired a shot that could pierce armour, though only at close range. In the 1500s, it had to be mounted on a support stick to keep it steady. The caliver was the lighter form of the arquebus. By 1600, or so, these firearms were phased out in favour of a new lighter musket. For most of the 1500s and 1600s, muskets were of the matchlock design. However, this was superseded in the 1690s by the flintlock musket, which was less prone to misfires and had a faster reloading time.
The Europeans adopted it from the Chinese and they started using it around the Song Dynasty. The sole person who invented the firearm is unknown.

Answer 2

The Chinese did many centuries ago