Travel within the city can be done easily by foot or bike. Public transportation such as buses, trams, and metros are also available and cost around €3 for a single ride. Taxis are also an option, but these can be more expensive.
If you have more time, consider visiting the Rotterdam Zoo, the Museum Boijmans Van Beuningen, or taking a boat tour along the river. If you have less time, consider skipping the Maritime Museum or the Cube Houses. Additionally, it's recommended to wear comfortable shoes as there will be a lot of walking involved throughout the day.