Hi!

I have a Teksumo wing that I am really please with. I have a 1950 kv motor installed and flying it on 4S. However, I do feel like I do not have the top speed that I want and I am thinking that it might be due to the propeller (I am using a 7038R propeller). I do have really good low end but after 75% throttle more or less nothing happens with the top speed.

How do I know which way it should be mounted and in which direction should the motor be spinning with a pusher setup?

The motor should spin counter clock wise as you're looking at it.
you must have a pusher prop. You cannot install a regular prop backwards and have it work.
as far which way a pusher goes on you have to look at the prop

Look at the prop's blade end on and you will notice they have a curved cross section, not unlike the sail on a boat. It's concave on one side, convex on the other (A propeller blade is basically an undercambered wing with a serious degree of washout). When it is properly mounted on the aircraft the convex side should be facing forward.

Actually Jetmech isn't entirely correct. Assuming the hub is the same on both sides, any prop can be used as either a pusher or a tractor (puller) prop because it doesn't care which side the motor is mounted on, so long as it's pointing and turning in the correct direction. With a brushless motor this is as simple matter of reversing the direction by switching wires.

ALL props must face the same way. Towards the front of the plane. Irregardless if they are on the rear or front of the plane. A pusher props blades have the opposite angle than a standard ( or tractor ) props blades.

The reason for a pusher props is for when they are used with reverse mounted glow engines that can only run in one direction. For example, a swamp buggy with a rear facing glow engine. For electric planes you do not need a pusher prop because you can mount a standard prop facing forward and reverse the motor if needed.

That's what I said. The OP already indicated he was using electric.

The 2nd comment cant be correct Pusher props are indeed different

Of course you can use a ordinary prop as a pusher prop...you just turn the prop around an run the motor clock vise (electric that is)

I does surprise me that we STILL seem to have this discussion about tractor and pusher props!
As stated for electric there is no pusher just CW or CCW rotation.
With IC a pusher prop is different unless of course the IC motor can rotate in either direction.
Of more importance for safety is the distinction between a prop intended for IC and one specifically for electric..