After playing many arena matches my armour is damaged. how do i repair it and if i cant how do i get new ones.
Also, is it possible to obtain arm armour as well as chest, leg, hand and head?
In the current build armor is not repairable no, to get new armor simply remove the pieces you have on that are damaged from your inventory and re-earn them fighting in the arena.
The only way to obtain Armour for your arms is to defeat the cumans for theirs (I think one of the chests in the military camp has some but its very difficult to pick). There is also a way to glitch a full set but it requires using the save function and more often then not makes the continue unplayable(if you want more details on this manipulation send me a PM).
Back to repairs, you can repair your sword which you can find the details for in this thread.