Responsive Stats Preview Card Component with HTML and CSS

I struggled with responsive design and even though it works for now I am not really sure if it is correct and need to some solid advice with handling images in responsive design. Media queries are not my cup of tea and so is working with images. I used the same desktop image for mobile responsive as using the picture element didn't make sense to me; I couldn't understand how to put the image attributes for the source element with the image and doubted if it would work.