profile card with html and CSS

Hello fellow coders! I tried to make my website as responsive as possible but may have failed. Where can i learn more about responsive design?No article seems to explain it well. Using pixels in my project was intentional because it didn't seem like the card looked different on mobile and desktop apart from the margins. Is my approach valid? Is using absolute units appropriate if a website is going to look the same on all devices such as this project? I also came across a problem trying to use the device developer tools. How do i stop the page from zooming in and out when changing the device width and height on google chrome?(i have tried switching off auto zoom). Your feedback is appreciated