Foreword: I am an Aerospace Engineering student and next year is my third and final year, starting September 2019.
I was taught approximately 2 semesters ago that the correct theory of lift is that airflow circulates around the wing and so the upstream increases the velocity on the top surface while reducing the pressure, and reduces the velocity on the lower surface while increasing the pressure, which causes a difference in pressure that generates lift. Prior to that, I had the incorrect, yet simpler 'equal transit time' theory, which I'm guessing is taught at all universities at the early stage due to the simplicity of it. My problem is that I still base a lot of things on incorrect theories of the production of lift.
What causes air to circulate around a wing, or even a cylinder? My answer to that would be due to viscosity and boundary layer effects, is that right or wrong? I'm honestly unsure.
Since this theory was first being explored by analysing a cylinder, and it was determined that a cylinder can produce lift due to circulation of air (and the direction of upstream air), why do we have airfoils shaped in the way they are? I have many answers to this question which now I'm honestly unsure of due to the mix of theories in my head and some are based upon incorrect lift production concepts. Please give me a detailed answer for this question especially.