Hello,
im trying to find a accomodation in Cinque Terre region for 13 people.
The best would be if we were together in one accomodation or in some close to each other, and the beach nearby would be best.
Any tips where to look for something like this?
Why not see what turns up on booking.com. It has listing for apartments and B&B-style places as well as hotels. You can identify options there, then try to find a way to book directly--which often saves money. I haven't been to that area in many decades, so I have no personal wisdom to offer.
Hotel Villa Steno in Monterosso has some 2 bedroom units and is well suited for what you are seeking. Plus, it is a wonderful hotel.