Customize a few things

Hi
I wonder, how I can customize some things in the theme:

* How can I set the background in a welcome-page appearing in the start-page to transparent (actually white) ?
* How can I change the width of the content-section of a page to make them wider ?
* How can I change the sidebar-background from transparent to a solid colour (i.e. white) ?
* How can I change the footer section – colour from blackt to another (i.e. white) ?
* How can I change the font-types of the site ? I tried “body {font-family:…” in the custom-css (Customizer) but it didn’t work …

Tnx in advance
Worels

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