>>928963

It may not need to be perpendicular to the longitudinal center line. Most planes have built in down and left thrust. This is to offset torque and the center of drag being higher than the thrust line respectively. Most high wing planes have down thrust. So don't assume it needs to be be fixed. Is that a factory install or did you install the motor?

It's not supposed to be. The motors make too much torque for the size of the plane. If there aren't canted properly it becomes uncontrollable or you need to use all your control authority just to maintain level flight.

>>928966
I assembled the airplane.
The problem is that because of being so inclined, the propeller touches the plane's body, and gets stuck, unable to rotate.

Is the shaft bent or is the motor just mounted that way?

If the latter, the solution is simply to remove the motor and add washers, shims or at worst rework the firewall to take out the excessive downthrust.

If the former, buy a new motor or at least a new shaft. Don't mess around with trying to straighten a bent shaft, it's not worth the trouble.