Open excel
right click on the blank area at bottom of ribbon, near where it says Clipboard, Font, alignment, etc.,
Customise the ribbon is a choice in the menu that opens
in the next big window that opens, at bottom right there is a heading called Customisation with a drop down button saying reset.
Click the arrow in that button and Reset all customization is the bottom choice
click ok
this fix would also work in word - you will need to do in both if you have them.
Office is the suite of office applications that excel and Word generally come with.
I don't know if that will help with that other problem you mentioned - the big menus.