I am assuming that your brakes are not working, rather than stopping too hard.

The GST brakes are good once they are set up.

there is a shaft coming from the throttle/brake servo that goes through two loops. On that shaft there should be two clamps.

Turn on your radio and receiver so that all the servos go to a neutral position. Then undo the clamps and slide each so that they are snug against the loops (away from the servo) and retighten.

Hope that makes sense.