Heres an explanation from a beginner:

Air is a mass. All airplanes have the ability to create thrust. With thrust, the plane pushes against the air (a mass) and the air (mass) pushes back against the plane. Wings are shaped to create lift, like you had described. With thrust, the orientation of the plane does not matter (whether it is upside down or not), as long as it is going in a forward manner. Am i right?