Two sims4 files after repair

@DeMosterdsoep  Some Sims 4 user data folders (the Sims 4 folder in Documents\Electronic Arts) are localized, meaning they're named in the language you're using to play.  So you probably have "The Sims 4" and "De Sims 4."  Which one the game reads depends on which language it's currently in.  This is normal, although there are only a few languages that get their own localization; the rest use "The Sims 4."

The saves disappeared because the game was reading the Dutch version, and they came back when it resumed reading the English version.  This is also normal, although it does alarm some people who switch languages.

There's no harm in deleting the Dutch folder, as long as you're sure you don't want any content inside it.  These folders or their contents are designed be swapped without issues.  If you decided one day to play in Dutch, you could change the "The" in the folder name to a "De," and the game would continue to use that folder as if nothing had happened.