Fonts are too big

      I am a novice at Linux. If you have advice, or an answer to my question, please give a full explanation, so that I may understand it. Please do not omit any steps in the instructions, or I will probably not be able to complete them.
      Ubuntu 15.10 laptop.

      When I use Unity Tweak Tool, it does not save the reduced font settings. When I restart my computer, the fonts and windows are huge, and I can't see anything, because most things are zoomed in like a microscope.