Weak Wifi (and GPS and BT) signal

A couple of days ago, I changed the back camera of my Honor 8. Since then, my camera is working fine again, but I can only connect to wifi when I am right next to the router.

I changed the white koaxial Antenna Cable and double checked with a multimeter that the outer and the inner cables have a resistance. The cables are correctly plugged in.

Also the two small springs are still attatched to the middle frame (I think they are also kind of wifi related).

Now I am out of ideas of what could be broken so I am asking for your advice. Would be great to get some help since a phone without proper wifi is almost useless…