Bochum is in the center of the Ruhr metropolitan area, which has to offer a wide variety of activities.
For a selection of bars and restaurants, the Bermuda3eck is a good starting point.
Having an industrial history with coal mining and steel production, there's also the route of industrial heritage extending through the whole Ruhr area and running through Bochum. It passes by places and buildings which have been or still are relevant to the industry in the area. It's great for taking a walk or cycling and to get to know some history.
For general information on tourist activities, see this website.
For events taking place in the Ruhr area make sure to have a look at Ruhrgestalten.
This instagram site provides nice photos of Bochum and the Ruhr area.