Making a responsive website takes a lot more than just designing. With Google PageSpeed Insights, you get all the help you need to create a fast-loading site!
In applications such as Photoshop and Illustrator, the graphics you make are fantastic, but frequently the file sizes are quite huge. If you posted these photos on your website, they would load slowly, and your target audience will leave your site. Optimizing your pictures is the key not to compromise the website load speed.