Book an apartment or home
Rentals are cheaper than hotels. You can go out for dinner, and there's plenty of choice to do so in Bern. But of course you can cook your own meals as well. There are a lot of supermarkets in Bern (look for Migros and COOP) that make shopping and cooking part of the fun.
Interhome offers thousands of holiday homes and apartments across Switzerland. They offer discounts on both early and last minute bookings. That makes the Interhome website a good place to start your search:
https://www.interhome.com/switzerland/: all holiday homes
https://www.interhome.com/switzerland/early-booking-discount/: find the discounts for early bookings
https://www.interhome.com/switzerland/last-minute/: find the last minute offers