Not quite right again.
Wing shape can generate lift depending upon the shape. Flat bottoms with curved upper surfaces in level flight create lift with NO (or little) angle of attack. Adding AOA increases the amount of lift until you reach a point where you actually stall due to seperation of the laminar flow boundary layer over the top of the wing. Symetrical wings generate lift ONLY via AOA and eventually stall for the same reasons.
Lift is created in the flat bottom version NOT because the air over the upper surface moves slower but because it moves faster. The seperated (by the leading edge) air mass wants to rejoin at the trailing edge. Since it is a longer distance over the curved surface than over the flat surface the air much move faster. This increase in speed causes a slight reduction in air pressure upon the upper surface relative to the lower surface. So you can say the upper surface is being sucked up or the lower surface is being pushed up, That point is irrelevant.
It doesn't take thrust per se, not much thrust in most gliders. Gliders glide DOWN and while doing so generate lift by moving forward. The lift must exceed the a/c weight for the plane to fly. To move forward you need to exceed the amount of DRAG the a/c presents to the air.
A flat bottom wing flying inverted MUST have a higher AOA to maintain altitude.