Greetings.

Often read "airplanes with 'high wings' are slower than airplanes with 'low wings'  Why ?

1 hour ago, Externet said:

Greetings.

Often read "airplanes with 'high wings' are slower than airplanes with 'low wings'  Why ?

Not a complete answer but my understanding:

Pitch axis torque from propulsion vs drag, and stability from the centre of gravity being below the centre of lift for the slower aircraft as required more so at lower speed.

You will generally find higher speed aircraft with wings more centred on the body than in the illustration where the body and structure allow it, but the low wing one illustrated would be lower drag at the same speed than the high wing one, which matters even more at it's design speed.

High wing aircraft tend to be more stable, as the mass is underslung, rather than balanced atop, the lifting surfaces.
I have heard of this called the 'pendulum', or the Keel, effect. Stability can be compensated for by other means ( dihedral ), so it's not really a deciding factor; other things, like length of the landing gear, or ,having to fuselage mount the landing gear in drag producing fairings, are.

On the other hand, most transport aircraft, or any other where access to the fuselage for loading from ground level, is needed, tend to have high wing mounting. This is usually done with a bulkhead accommodating the carry-through structure, so it is a lot stronger, and doesn't need the drag inducing struts/braces, as in the above pictures.