Serial comunication with Arduino Mega - Serial monitor problem

[A_P1]

App is remote control for GPS guided trolling motor for my boat with spot lock function to keep me in position on the sea.

Arduino is the brain, and App is the remote and memory of spot lock coordinates as backup.

[ChrisWard]

OK, I think we are getting somewhere

This is what you said in your first post:

@A_P1

I have problem with receiving serial data on serial monitor in Mit App application.

I need to receive different Serial1.print() data from Arduino thro Bluetooth, like different commands and sensor data: Left, Right, Distance from GPS point, Heading of compass,....... and so on.

So if the App is the remote control, it should actually be sending commands like Left, Right and so on, not receiving them?