Cecil
I can tell you the type of mission you describe is quite easy except for having trees close by.
The GPS signal depend on how dense the leaves are on the trees. I fly between trees and see only minor problems with GPS but the trees are old and the canopy thin.
Here's a mission that is the best I have for being like the mission you described.
https://www.youtube.com/watch?v=czeAn1vKbag
I did that one when I was just starting to do missions and the motor mix was not the best.
Larry