Change grid interval and specify tick labels

I am trying to plot counts in gridded plots, but I haven't been able to figure out how to go about it. I want: to have dotted grids at an interval of 5; to have major tick labels only every 20; for the ticks to be outside the plot; and to have "counts" inside those grids. I have checked for potential duplicates, such as here and here, but have not been able to figure it out. This is my code: impor

[dynamicsoar]

なるほどなーこうやって描くのか。助かるわー