Hello Dniel109, and welcome to the Unreal community.
Congratulations on making great headway with your landscape. I agree with your initial assessment in that the edges do look a bit jagged. I found a very detailed, lengthy thread that has a multitude of solutions.
Some of the subjects are about: Smoothing the landscape, checking your FPS to ensure it is within a reasonable range, using tessellation and much more.
Here is additional reading material on Landscapes if you ever feel inclined to do more reading into the subject.
I hope this information helps.