I figured I'd post this since most in the industry use excel every day.
Two problems:
I use a laptop with windows 8. When I was adding columns to a worksheet, I pressed (Fn)+ F4 to add a ton of columns. My laptop requires me to press the Fn key to freaking use any of the F# functions. I don't know if I exactly pressed Fn F4, but basically, this made my ribbon extremely huge. I can deal with it, but it takes up like 1/3 of the screen when I'm doing some sort of shortcut that involvest Alt + [random shortcut here]. My laptop is touch screen, but I've already unchecked that option from the ribbon, so that is not it.
Also
Whenever I copy paste an entire worksheet (say appprox 60 rows and 30 columns) and paste it into another worksheet within the same book, the whole workbook gets really slow. After that, if I want to add a column, an error saying that the action would take too long pops up. Saving the file also takes a lot of time. What is the problem with pasting worksheets?
I think I'm using Excel 2014 (Microsoft University 365, bought it last september).
EDIT: Apparently Paint has also oversized ribbons. This seems to be system-wide, but it all started with Excel. The formatting options take the whole spreadsheet length-wise, as seen in the 2nd pic.