How can I change the gray area amount in the normal view? I accidentally clicked something (don’t know what) and now, when I start the program, there appears only the gray area in the view (without the ruler at the top) and I am not able to see the white page at all unless I scroll the sidebar at the bottom. The gray area is on the left and the page on the right.
Switching off the program & the computer didn’t help.
Thank you for your help. 
Not sure where you are.
Open the View menu. Make sure that Status bar is ticked. Look in the right bottom corner. The number there, like 300%, is the zoom indicator. For now, set it to 100% with the slider directly to the left. More to the left are a few tools to control the number of pages displayed on the screen. Play with them. Make sure that the rulers are on as well (View - Rulers).
Thank you! The problem was with the number of pages displayed on the screen. Problem solved!