I created a basic form

Any feedback, best practices, and suggestions are fine.

good bro it is looking greet

It looks good @Aclixion. Some things to revisit;

  • The form should throw an HTML5 error if the user does not enter a username and/or password and clicks the submit button
  • Change the cursor to a pointer when hovering over the submit button

What about the CSS though? Is there anything I should change or are there best practices I could follow?

  • Rather than using fixed dimensions on elements, use max-width/height and relative units like %, em, rem and vw to keep everything responsive.
  • Provide a default fallback font. It’s possible that not every OS will have the font you specify or if calling a font the call may fail.
  • Style for user’s that use the keyboard to navigate.
    For instance, there’s a hover effect for the submit button. Provide that same effect for someone that’s used the keyboard to get to the submit button.

Something else I noticed on looking at your form a second time.
When the user types in a password, it should not be shown in plaintext. This would be a bad UX. Hide that password.