Consider this carefully...
nobody here will help a wise cracking cool dude that can't even be bothered to use proper written english, or as close thereto, when they come here to ask for help with something...it confuses matters no end when english is not your first language.
You could do it with a changeover relay, a small hydraulic pump with reservoir, a couple of shut off valves and a small ram with ball end fittings and a couple of pivot points.
Or
a changeover relay, a long stroke solenoid capable of pulling as well as pushing with suitable pivot points and mechanics and a couple of limit switches.
Or
if you arrange the pivot point for the flap so that it is not at the bottom but rather is offset a little, you could fashion some sort of lever and toothed belt drive using a stepper motor, control electronics and a couple of limit switches.
Personally I would prefer the first solution, because it's easier, but both the first suggestion and the last one will allow you to regulate the speed at which the flap moves quite easily. The solenoid idea will require to have a damper fitted to control it's speed.