A group of erasmus students trying to find an apartment in Sofia

Hello, my name is João Pinheiro and I am looking for an apartment for me, my girlfriend and 2 friends. We are from Portugal and we are going to study in Sofia under the Erasmus plan. We are trying to find an apartment between the NSA (National Sports Academy) and FEBA (Faculty of Economics and Business Administration), We are going to stay in Sofia for 5 to 6 months and we are prepared to pay for an apartment for 300 to 400 euros. Hope to see some fast response, because we are in desperate need of finding a place to stay