I am in your Magento Admin.
Sorry but, the theme don’t have errors. Your Magento is misconfigured.
1. Categories: you can’t see the categories, because you haven’t the cateories in Default category.
2. You don’t see the slider, because you didn’t configurate the Layout as homepage.
3. You don’t see the products in homepage because category_id=3 not have products associate and the only product in the store is “Out of stock”.