Sims 4 Legacy Edition Removed my gameplay!

@madeleineross  The Legacy Edition reads a different user folder than the standard version.  If you look in Documents\Electronic Arts, you should see a "The Sims 4" folder and a "The Sims 4 Legacy Edition" folder; the two will have different contents, with saves from one version not crossing over to the other.  Your saves should still be intact, but even if you moved them over to the LE folder, you probably woulddn't be able to open them: saves from the standard version contain content not included in the LE.

The real question here is why you were prompted to install the Legacy Edition in the first place.  If you've been playing the standard version, your computer wouldn't suddenly require the LE; it's more likely that your antivirus quarantined TS4_x64.exe and Origin thought you couldn't run it.  The usual fix for this is to disable your antivirus, repair the game in Origin (putting back the .exe), and then set exceptions in your antivirus for TS4_x64.exe and Origin.exe.

If the above doesn't help, please let me know what antivirus you use.