Galaxy j5 2017. It's network signal capture is very weak What can I do to boost the signal?

[AC Question]

I am living in Greece before I had an iPhone 6 but I lost it. I purchased a J5 2017 but it's signal especially 4G is very weak and cuts frequently however the other types of mobiles don't have this problem.

 

[B. Diddy]

Welcome to Android Central! What's the exact model number of the phone, and which carrier are you using? It's possible that the phone doesn't support your carrier's main network band, and therefore gets only a relatively weak signal. There wouldn't be anything you can do about that, besides change your phone or carrier.