Welcome Enzo.
- most people use a LocationSensor to determine their current location
- every 10 seconds? Why so often?
- why are you using a List (called 'List') to store location coordinates. to almost 14 decimal place precision?
- your Button1 always sends the position of the first coordinates in the list. Is that what you really want to do.
Here is a way to send a location to a CloudDB (similar to a FirebaseDB) How to broadcast a GPS location and share the information on a map with others in real time..CloudDB . The example might help you do what you hope to do.