How do I add a full meal?

To start tracking, tap the "+"-icon in the navigation bar on the dashboard.
0. You will automatically be taken to the "Food" tracker
1. First name the dish (e.g. pizza)
2. Then add the ingredients (e.g. cheese, tomato sauce, etc.)
3. Add a drink to your meal (optional). There is a separate category for water.
4. Add a photo (optional)
5. Tap "Add dish to favorites" if you want to save the meal for future reference
6. Tap "Save All"

You have 13 different categories to choose from, such as stool, digestion, mental, medication, and many more. 
I want to start from scratch and delete all entries. How does that work?
How do I edit already entered data?