Variator means something totally different.
What you have here is a teardown of a so called motor driver or motor controller - most likely a brushed DC motor driver.
Designing it to work again is much more than just a gate driver and a FET, because it's not just a PWM module, but a motor controller, which is more complex. For example, it most likely needs an active current limit or current mode control. Luckily, there is a lot of information and it's not an impossible task now that you know the right search terms.