Renting/subletting apartment in Barcelona

Hi all,

I am considering going to Barcelona for a Spanish language course in january. Wanted to go to Guatamala first but figured why fly far if what I want to do is learn Spanish and not see things there neccesarely. I was wondering what my best options for renting/subletting a room/apartment would be. Also what a realistic price range is for 3/4ish weeks. The location of the school would be in the city center.

Thank you for your help in advance!!