Re: There's a problem with your download - Something went wrong during your down

@tratzum  I've moved your posts to the Sims 3 forum for better help.  Please do a clean uninstall of Sims 3 and the EA App.  Start by uninstalling Sims 3:

• If you have a Sims 3 folder in Documents\Electronic Arts, put it aside and rename it to something that doesn't include the words "Sims 3."
• Download Revo Uninstaller (the free version is fine) from here.
• Launch Revo, select Sims 3 from the list, and click Uninstall.
• Once the game is uninstalled, select "Moderate" under "scanning modes," and click Scan.
• Review the list, in case there's something you want to save; otherwise, click Select All, and then Delete.
• Close Revo, and restart your computer.

Uninstall the EA App with Revo as well.  I don't have a walkthrough for that right now, but it should be straightforward.

Restart your computer and reinstall the EA App.  Create a new folder on the root level of the drive of your choice, for example C:\Games is fine, but not C:\Program Files\Games.  Install Sims 3 into this folder and see whether it works.

If you use a third-party antivirus, please leave it disabled for the entire process, including when you try to launch Sims 3 if you get that far.   As long as you're not doing anything else at the same time, your computer should be safe.