Can I replace the Bluetooth module from 4.0 to 5.0?

Sadly, there is no newer AirPort boards for your system (Bluetooth 4.0). Your only option is to use an external USB adapter, just make sure macOS is supported.

You may have a simple problem as the Bluetooth antenna line could be damaged and all you’ll need to do to regain the signal strength is to replace it. Its still a bit of a job as you need to remove the lid to following this guide Sostituzione gruppo dello schermo MacBook Pro Retina 13" metà 2014 as you need to get the black clutch cover off as the antennas are underneath it MacBook Pro 13" Right Hinge, Antenna/iSight cable