Changes in Mobile are Affecting Desktop

I have watched the breakpoints video ten times and I know everyone says that edits made on Mobile do not affect desktop, but they do. I have spent hours trying to figure out why I can’t edit the mobile version of the website without it affecting the desktop version. I see at the very top of the Style tab under “Selector” it says “Inheriting two selectors” and if I click on them it says it shows the desktop symbol. How do I turn off the inheriting selectors for when I am making changes on mobile so it doesn’t affect the desktop?

Below is my read-only link to show you what I mean. Because I can’t fix any formatting issues on mobile without it ruining my desktop version, thank you in advance to anyone who can help me with this quickly so I can have it done for my customer soon.