Can't change speed with a L298N

Other Hardware Motors, Mechanics, Power and CNC
1

I want to use a L298N to control an electric motor.
When the protection for the ENA pin is on, the motor run, but without me beeing able to control the speed.
And when I take of the protection and conect the ENA pin to my MEGA, the motor stops and refuses to run.

I've tried 2 differents L298N with the same problem.
And I've also tried with the ENB and same problem.

Do you have an idea why I have this issue ? And if so, how can I fix it ?
Thanks for your help.

2

You missed to connect ENA to an Arduino PWM pin, whose duty cycle will affect the motor speed.

3

Instead of writing so much explanation you could have shared a schematic. Now we have to guess and this is not our strong point - after all, we are in a forum for electronics and not for psychics. Do you have a common ground connection?