Are you annoyed because your streaming of Netflix, Amazon, Maxdome, iTunes, or your media centre stops, is choppy, or stops and starts, even though your internet connection should be fast enough?
Your WLAN is probably the culprit.
No matter how good WLAN is: it can’t do magic. If there are too many ceilings and/or walls getting in the way, its quality can worsen. Also and especially when multiple devices are using its services at the same time.
The solution: Make use of the two existing wires of a phone line or antenna cable and convey services from the FRITZ!Box/router to the TV through the two-wire LAN system.