do you know how to fix it please?
The problem is that you’re clicking on something that is outside the navigable area as setup in your NavMesh. With the click and move system that is in-place, the pawn will attempt to reach the exact spot you clicked on, unless that target is invalid; which is what the wall is causing it be viewed as.
I’m sure there are multiple ways around this, but the only one coming to mind at the moment would be adding an IsValid? check after the click location but before the move and if the location isn’t valid, then have your pawn move towards that location but stop at the edge of the navigable area.
NavMesh is big and tall enough. It would be enough for me to hold the right mouse button to run the character in that direction and bypass the simple structures and after the key stopped moving but i dont know how 
You need to make walls a bit wider so that you get a bit of navmesh on there. Then it will work as you intend. I just tested this quick time so there may be a better way.
yes with the walls it helped. but how with tree ?
Collision Setup on meshes.
Present custom:
Visiblity-> Ignore
Uncheck: Can Ever Affect Navigation
Problem Solved.