if there is no oxygen around the sun then how does the sun burn is the sun really burning can the process be called combustion

The process in which the sun releases energy is through a process called nuclear fusion. In it's core hydrogen atoms fuse into helium atoms, (this of course is hard because 2 protons repel each other and for this to happen it requires a certain amount of energy and velocity when they collide, this is only possible because of the gravitational pressure at it's core). In the process of fusion a little bit of mass which gets converted into energy.