Simple design using HTML and CSS

As a beginner who is still learning, I took the leap of faith to try an actual challenge.

1. I think I made a mistake by including the image in img tag in the html file because now, I can't change the image based on screen size. If I add the image as background, then how can I set it on the left side as shown?
2. And the original price and discounted price in the unordered list items were going off the border. So I had to hack this and that to get them to the correct position.
3. My codes are a bit messy I know. Any suggestion how I could improve it?