U must first couple the motor driver with the Arduino pwm pins.
Create a code using switch operator(i had done it tat ways and found it to be the most elegant.) u can use if else also.
Check hc05 for its AT commands and ensure its proper working.
Then test the bots movement using serial monitor.
Then use bluetooth terminal app to check the proper functioning again.
If all works fine, make ur own app or use something like Bluetooth rc controller to make it work! Good luck! 👍✌️