I made a cross section and the result is a vertical line not a straight line to the side. What should I do to fix it?

[BaktiarSianipar]

[DanPatterson]

What is the coordinate system of your X and Y?

If it is a projected coordinate system (ie.  Meters), then your Xs are showing increments of  millimeters. is

If it is a geographic coordinate system,  then X and Y are not planar and you should project the file to get X, Y and Z in meters assuming Z is in meters