I have 2 pages:
Both of them have a style class with the same name '.Grid'.
When I'm in the CreatePost page and go to the Home page then the Home Page keep the .Grid from the CreatePost page.
Should not the styles be removed when the React functional component is unmounted (when I exited the page)?
I'm importing the styles like 'import ./Home.css' and 'import ./CreatePost.css'
React won't remove the CSS you import, since it is not React component. You can consider using styled-component.