GPS not working properly on iPhone: it knows where it is but app can't recognize it
It can’t hurt to open 1 GB of free space, but your GPS is more likely an issue with location services. 


Get a good backup
Disable location services entirely and power down the phone 
Power on and enable location, verify cellular data and WiFi, bluetooth, data and cellular radios are on. 
Try maps to locate and walk to be sure GPS is tracking 
Take some photos


If you still are not getting gps in other apps, consider deleting the app (reminder about backup) and reinstalling. Also, check location for that specific app. Toggle off and then on. Restart. Then consider erasing the device and testing then erase and restore your backup. 

Only other item is reset network settings ( know WiFi passwords are deleted from f you do this and second reminder to back up just in case ).