22 year old guy, looking for accomodation in Donostia-San Sebastian

I'm a brazilian physics graduate student, and I'm going to be in a research internship at the DIPC (Donostia International Physics Center) during the period of April to October 2020. I'll be working most of the day, and I'm a very organized person so you should not worry about that. I wish to find a modest accommodation, with a price not above 500 euros and which has the same price during the summer. I would prefer to have a private room, but I woud not discard shared rooms, especially if the price is attractive. I thank you all in advance for any help and advices you may give