I’m using Nirvana with the WP Google Maps Plugin. The Plugin has it’s own CSS files but some of the CSS setting in the plugin are overruled by the inline CSS-Code from Nirvana.
How can i put the Nirvana CSS-Code in a .css-File?
You can copy-paste it to a CSS file (which you enqueue – perhaps in a child theme), but then any changes you do in the settings in the future will be overlapped by the ones saved in the file now.
Plugins should load their style correctly, when they don’t they are poorly written.