KayraBey91:
When I use standard serial pins (Hardware Serial) how can i define BTserial? Like this;#include <SoftwareSerial.h>
SoftwareSerial BTserial(19, 18);
Without SoftwareSerial how can i define BTserial?
Assuming you want to use Serial1:
HardwareSerial &BTserial = Serial1;
If you want to use a different serial port then you just need to change the last part.
There's no magic in renaming Serial1 to BTserial, it's just giving it a different name, which maybe would make your code easier to read.