, is there a way of "pluging up" the cavity of the removed door, so the car will become two door coupe

dont be silly, technically it could be done if you wanted to spend around $10,000 on the car. If you PLUGGED up the back doors how would you get into the back seats?

Sell that car and buy a two door, problem solved!!!!!!!!!!!!!

you could try braking really hard in front of a lorry!