Desktop Optimisation

i’m a having a trouble with my desktop optimization. i’ve build a mobile optimized website and now when i start building my website for desktop, it’s all altering my mobile optimized website content, if i do change any on desktop version ,it effects mobile version ,respectively

Need help urgently

I’m sorry, but you’ve worked backwards.
You need to start with desktop. That’s your default breakpoint.

Any styles you do on desktop cascade down to tablet, then mobile.
If you make on override on tablet, then it cascades down to mobile.
If you only make an override on mobile it doesn’t cascade back upstream.