Bluetooth communication with MIT App Inventor 2

SoftwareSerial won't work at 115200 baud. 38400 is the best it can do I believe.

If you can't change the Bluetooth baud rate then maybe you could connect the Bluetooth device to pins 0 and 1 and use a USB-TTL cable connected to the SoftwareSerial pins to communicate with the PC at 9600 baud.

Or use an Ardduino Mega which has 3 spare HardwareSerial ports.

...R

PS. please post your program using the code button </> so it looks like this. See How to use the Forum. It makes it much easier for people to help you