You can use a new module for automatic translations of your website.
New pages, blog posts and changes are automatically translated.
apps.odoo.com/apps/modules/18.0/website_aitrans
(Also for Odoo 16 and 17)

Hi George,

I already experienced the same issue and also involved the odoo bug team at that time.

the issue came, because at the beginning we made the page with main language "english" but then one day decided to make it German as main language, so we switched. And this switching confused odoo and we had the same issues with the translations.

When i changed only minor things in texts, odoo created a completely new entry in the background. there we some sentences, where over the time i made 4 changes and therefore had 10 almost duplicate entries of it (hard to explain without screenshot, sorry) - 5 in english and 5 in German. usually when you chance minor things, odoo does not create a new entry but rework the old one.

I'm talking about the entries which you find in the website module -> Site -> pages -> bug symbol (gotta be in the developer mode).

there you see the view with the architecture of the page and on the right side you can see a small "EN" or "DE" or whatever language. When you click on that, i will open in a pop up all the translated terms and fore sure you will also have a lot of duplicates there.

sad truth: the only solution i found was reworking the whole website.

I'm not sure anymore if it was sufficient to work page by page (so delete the whole page and create it new) or if i had to delete the whole website and start again- its some time ago, sorry.

But maybe you can, before you do that, export all of your translations from the website and then import them again - you would need to test that by your own.

Just to make sure there is no problem with your database try duplicating it and try to make the website's main language as "English" and the translate every term to Dutch. Or create a new database for test purposes.

Odoo highlights the translations with 2 colors green and yellow:

Green is for translated terms.
Yellow for untranslated terms.

So you have to translate every paragraph on it's own not the whole page at once.
After you test everything and everything seems valid then apply it to your main production database.