Fihaonambe Fanampiana Firefox

HI After using Chrom for num of years I have now reverted (upgarded!?) for Firefox. However what's casuing me to regret my decision is the layout og Gmail in the browswer. Most of the labels and text are surround by a white Highlight or box which looks ugly. I have exhauste dverything I know to get the text to look like Gmail in Chrome with no success. See attached screen shot of comparison. Could you please give some idea so That I can stay with Firefox Kind regards Chris

This post is on my Mac Catalina. This morning Firefox updated on my Windows 7 before I closed out. Now that it is evening Firefox does not open on that computer. What should I do to fix it since it does not open; it crashes immediately.