I need a Coder who knows C# to help me on a small project!

I have to create Custom Methods for this project that might require foreach loops in some. I'm just very lost and I'm getting stressed because the deadline is approaching very fast. The scenario for the assignment is creating a Point of Sales. There are comments telling me what to do for each method, but I'm still confused. Below is pictures to help explain.


Tax is 7%

Here is the values for the list item collection:
Blueberry - 2.75
Cheese - 3.25
Everything - 3.50
Jalopeno - 2.50
Plain - 2.00
Wheat - 3.00

Here is the Values for the ListItem of Addtional Options:
Cream Cheese - 1.00
Nutella - 2.00
Toasted - 0.50
Peanut Butter - 1.50