Welcome to the forums @sulsoyy. Your page looks good. Some things to revisit;
Verify your email addr with codepen so we can see your page full view
Codepen provides the boilerplate for you. It only expects the code you’d put within the body element in the HTML editor. (No need to include the body tags). For anything you want to add to the <head> element click on the ‘Settings’ button, then HTML and add it into the ‘Stuff for <head>’ box.
What you have in the style element in the HTML editor can be placed in the CSS editor (without <style> </style> of course)
Run your HTML code through the W3C validator.
There is an HTML syntax/coding error you should be aware of and address.
Since copy/paste from codepen you can ignore the first warning and first two errors. (The other warnings are regarding semantics. You can review them but you don’t have to correct those right now.)
Do not use the <br> element to force line breaks or spacing. That’s what CSS is for.
Reference MDN Docs