Working to change and save my theme changes

I have amended the Fixer theme three times and saved my changes along the way. Then saved at exit and then exited UPFRONT. When I view my site the changes are all lost. Am I missing a step? Lost all of today's work? Any thoughts?

Also I am using Firefox as my browser and it seems to operate slowly at times and then at times it freezes up. Running Windows 10 updated with new pc and updated Firefox. Are there compatibility issues with Firefox and Premium themes?