Intro section with dropdown nav

• svg, I needed to darken the dropdown arrow and end up using 'fill'. It filled the icon completely instead of just the arrows line. Is there another approach that could achieve this? Is it also best to use svg tags within the HTML file itself or as 'background-image' in CSS?
• Is it best practise to add media queries (CSS) after each class or handle all media queries at the end of a CSS file.
• The nav I handled by using JS to swap out CSS classes (top nav to side nav). The HTML wasn't changed, its structure contained within one HTML element. Is it better to separate the side and top nav structures into their own html tags?
• The picture HTML tag am still new to. Seems difficult contain the image size for responsiveness without stretching the image out or being too small.

Any feedback on this or anything else would be great. Thanks for viewing