For the capital,, Bern is a rather small city, but, like any normal capital, it is filled with people rushing somewhere. The historic center is small, for some reason trams and buses run on it, and this, especially trams, does not paint it at all: the narrow streets are entangled with wires, and tourists all the time strive to get under the wheels.
A couple of hours will be enough to inspect the center, to which, if you wish, you can add a museum or a zoo, a botanical garden, a thermal pool.