Add this tag so that the browser will use your responsive styling. Without this, a mobile browser will used a zoomed-out version of your desktop site.
Instead of using pixel sizing, use percentage sizing wherever possible. Percentage sizing can be used for layout elements. It can not be used for text.
Combining a pixel max-width and a percentage width gives you full-width on mobile and limited width on desktop.
The vh measurement is like %, but it’s a percentage of the view height not the container height.
Using this setting will allow your background image to re-flow to fit any container size. Make sure to consider how the image could be cropped when choosing the image.