Everyone is focused on lens issues, which will solve the exposure issue. But if you look carefully, these original photos are more than just underexposed.
Until the camera is held still and shot is focused properly the same original problem will still be a problem in a better exposed photograph, no matter WHAT glass is on the camera body.
I can take my D80 or even my "lowly" (as some here seem to feel that they are) D40 and kit lens and get clear, in focus shots of what OP is trying to photograph here.
Look at the unfocused areas of the original photo, how will a faster lens help the focus?
Look at the blur, like the double image in the details around the window panes, how will a faster lens help OP hold his camera still?
Am I the only one here who sees in the OP that the camera is not focused properly, and that there is movement of the camera while the shutter is open?
What good does it do him to buy a better lens until OP learns how to operate the camera properly?