There are different ways to make contracts for your TV. First, you have to find out which kinds of services your TV provides and what kinds of additional technical equipment you might need for a given service. There are satellite TV, cable TV and TV via internet to choose from. For certain internet services, you need a given data speed. Please ask your internet provider, if the needed speed is available. You might live in a part of Germany, where the internet is not fast enough. If you want to install a device for satellite TV, please ask your landlord in advance if there are any regulations concerning this. There may be no way to install a satellite TV device, that operates properly.
You have to pay for the public television and radio, even though you might not want to use them. For details see: https://www.rundfunkbeitrag.de/welcome/index_ger.html