Cannot find styles - Where is the Style Sheet?

The appearance of an EE site is determined solely by the CSS applied to the site - EE itself does not mess with how the site looks.

A quick squint at your site suggests that you are using primarily a css file located at /css/style.css to control the look of the site, and I suggest you begin your search for where / how to edit with that file.

It looks like you use a lot of other vendor CSS files too and a number of element level style over-rides, so it might be more complicated to get the look you want simply by editing the main file.

To fix the footer, you'll need to remove one of the element-level style overrides - currently the footer layout is controlled by this tag:

<div class="container float" style="min-height: 643px;">

Which suggests whatever else you have set in your CSS file, the footer is going to be at least 643px high...

Good luck with your edits.

PS - If you get stuck with the ExpressionEngine implementation itself you'll make it easier for others here to help you if you include details of what version of EE you are using - there are major differences between EE2, EE3, EE4 and EE5 which affects how you fix some issues.