If your Wi-Fi or Bluetooth stops working, the signal is weak, or you have to wait forever for a page to load or for a device to pair, it's a pain, but it's easy to fix: Just replace the Wi-Fi/Bluetooth antenna on your iPhone 5S with a new one.
After that, you're sure to have a good connection.
Compatibility iPhone 5 (A1428, A1429)
Scope of delivery
iPhone 5 W-Lan antenna