It’s very hard for me to view your website and pinpoint everything that’s causing the website to malfunction if you or someone else changed the code. Best would be to install the theme you downloaded from themeforest next to your current altered theme, and make make the code changes again, step by step. All your content will still be there so don’t worry. You can install two version of the same theme by changing the new theme folder name to ‘therestaurant2’ for example.
Hope this helps!