Only save changes on the computer

I designed a site in the last hours, but I began with my site for phone and not with the layout of a computer.
Now I would like to edit the layout for the computer, but if I change something, the design of the phone change also. What can I do to only save my changes on the computer? Would it help if I work with combo classes which I only use for the computer layout? Of course I share my read-only-link if somebody needs it :smiley:

Thank you very much :slight_smile:
Finn

And sorry for my english skills :open_mouth: