Changing https:// to https://www.

Hi,
I changed my url from https://domain.de to https://www.domain.de in wordpress. I also replaced it in my database. But when I call the site with "www" it does not show me my old widgets in the sidebar. So I have to add them all. And it does also not show the original design of the WP Show Posts from Dispatch demo. Is there also a place via ftp where I have to change something? Then for example my css for h2 in my widget area is not working. Maybe the old domain is also somewhere via ftp reachable