What is below br2 and what is its role here ...i think it's acetic acid ..

see

Bromination of ketones occurs smoothly with bromine in acetic acid. The first step occurs in a cyclic way resulting in protonation of the carbonyl and formation of the enol occurri...

here in presence of acetic acid bromination takes place at alpha C of carbonyl group. Here first enol is formed in presence of Acetic acid then substitution of Br takes place. Simi...