Add force forward no matter rotation

So apparently if I rotate a sphere and I try to add force forward, the forward vector isn’t pointing forward anymore so the force gets added in the wrong direction.

I tried using this to rotate the forward vector and put it in the right direction, but no success:

Vector3 perf = transform.forward * 5;
perf =  transform.rotation * perf;
rigidbody.AddForce(perf

How should I handle this?

Vector3 myForward = transform.TransformDirection(Vector3.forward);
rigidbody.AddForce( myForward * 5 );