If you're expirencing some errors with overrides that you (or some modules) applied to your PrestaShop and if your shop is broken because of this - check this videoguide. You can easily disable all overrides with your back office features. It's great way to fix shop and make it working again (especially if we don't know how to fix the override bug).
Disable all PrestaShop overrides
Now your shop should start to work again, but it's worth to mention - this is not a fix to broken language. It's a way to make your shop working again without overrides. Great way if we are in hurry and if we broken LIVE shop.
How to disable PrestaShop overrides?