'Delay command' and bluetooth communication problem
I see 2 problems with your code:


You use the delay() function, which is not good coding style, since it is basically busy waiting. The Arduino will do nothing in this time, also not reacting to any input. Instead you should use a non-blocking coding style, which only does something, when it is time to do so, and will not block until something happens. You can see this style in the BlinkWithoutDelay example, that comes with the Arduino IDE. It uses millis() as a time measure. Think of how you would bake a pizza. You would not sit on front of the oven doing nothing, until the pizza is ready. You would do other things while looking at your watch regularily, checking, if it is time to take out the pizza.
In the Serial communication part you use parseInt(). That can be a problem, since it has a timeout of 1s (standard value). Until the timeout the function will block. This is mitigated, if you consecently send a non-digit character at the end of every value. But it is better to first read a full message (until the newline character \n) and then process the message as a whole.


Also the line if (bluetooth.available()) is not necessary here, since the while loop will do the same.