Hi, just got a used mini cooper s 2015, it as 15k mils

When I got it, only issue it as is the suspension, because the car was hit by the passenger side, so the lower arm, got bend and had to get the auto guy to have it straight out the lower arm, and everything was fine.

But after the change and a bit of long-distance drive, I notice that anytime I change the gear, it jack and shake a bit, this happen all the time.

So wish to know, what is the cause, is it the lower arm, should I get a new lower arm, to replace the one that had issue OR maybe is the Transmission Fluid should be changed or maybe there may be other cause of this?

Am using the car oversea, and not much people use mini cooper, so there is not a super professional auto shop that can help with this