@SparkieA I don't think it's too bad, but you've certainly got some organizing (and understanding) to do here.
Some steps first:
Click the Set as Default Browser to get rid of that bar. Or uncheck "Check on startup" and click the X to close it.
Then read:
https://help.vivaldi.com/desktop/appearance-customization/edit-toolbars/
Then edit the toolbars and remove the spacers to left/right of the address bar. The centered address+search fields are a new thing, but easy to remove.
Then to the Start Page. Read here:
https://help.vivaldi.com/desktop/navigation/start-page/
These things are Speed Dials:
fa5d5160-9249-4473-9dce-9d1a7d870531-image.png
They are folders of bookmarks set as Speed Dials. To remove simply right-click and choose "Remove from speed dial".
You can tell what folders have been assigned as Speed Dials by looking at the icon, the little square icon bottom right:
4538e1a7-e3ea-4b2a-80ae-f4368048c8ca-image.png
And then begins the big cleanup job I can't help you with.
You have several "New Folder" set as speed dials. As well as several duplicates (looks like).
You have to go through your bookmarks, clean up, remove duplicates and give folders proper names to get a structure you can understand and work with.
When importing bookmarks, they end up under a folder "Imported", it looks to me you have one at the top there. Generally when importing bookmarks, one would then move them out of "Imported" and organize them where they belong in whatever structure you've decided on.
Please familiarize yourself with the Bookmark Manager to better organize your bookmarks:
https://help.vivaldi.com/desktop/bookmarks-speed-dial/bookmark-manager/