Format the axis of the charts

Hello everyone!

I have a "stupid" problem.
For years I work with Excel and charts.
But this time, I cannot change the scale of the horizontal axis.
I want to put 5 in 5 (0, 5, 10, 15, 20, 25, 30, 35).
I checked previous files and I can change easily the scale of both axis, put the minimum and maximum value, etc...
But in the case I cannot find these options on the horizontal axis format...
It's because of the new version of Excel?
Thousands of data?
I hope you can help me...
I attached the file.

Joana

Change from line to scatter chart