iPhone didn't get any cellural signal and couldn't connect to my carrier so I desided to change the antenna to new one and it's working now perfectly. Now it connects to my carrier again.
I followed up your guide about changing cellular antenna and everything went nice and smooth.
I would give some very simple hint. Before you start to tear your device apart you should make sure you have piece of A4 paper and mark there spot for every screw because it makes the assembly lot easier. for example almost every screw in iPhone are different size.