How can I fix my cellular network?

Hey guys, recently bought a used black 32gb iphone 5 for 220€. I just get &&^&@@ in the ass, the back camera and the cellular data didn't work great, just got like 1min of data each 2 hours, even if the iphone can detect my career signal : http://imgur.com/j4MWxIN . I can't send/receive any message/call and the 3G/4G doesn't work.

I've ordered a new camera and new antenna for ~20€ (this one : http://imgur.com/4ZTd10i ). So i had to totally disassemble my iphone, and put that new camera and antenna. (The old one semmed broken : http://i.imgur.com/t4pREem.jpg) .

Right now, the camera work again, but still no cellular network... Is there any other part in the iphone that is fixable that could involve that problem ?

I've learned about this part, a second antenna, too : http://imgur.com/ycWGAME .

I've tried to boot with that part removed this to see what happenend : the iphone could find my career but still not receive a great signal and could'nt receive/send anything, so, same problem. Is this part that can cause a problem ? Is it just broken ?

I could go to a "professional repairer", but it would cost me 40€ to fix an antenna problem. Can someone tell me what should i do ?

Thanks !