No or very low cellular signal - which parts?!

After i repaired my screen the second time my cellular signal was very low or completely gone. I searched forums to find the parts that are responsible for cellular signal.

So i replaced the following parts:

- blue antenna cable
- gray antenna cable
- flex-platine cellular sub

Now i have a bit more signal but mostly NO signal :(
2 clips from the middle frame are broken (where the antenna cables snapped in) ... could this be the reason why i have nearly no signal?

I have no idea which parts i could replace to get my cellular signal ok. :( Please help!