Ok now let me give you a basic idea how this should be developed.

1. Get all the Menu Items and prices into a .txt file

   eg: - Fried Rice 180
   Fried Noodles 200
   etc.

2. Using file reading function read them at the start and get it into a 2D array and print them accordingly.

   it should be showed to select. (This may vary according to user's preference)
   eg:-

   1. Fried Rice - Rs. 180
   2. Fried Noodles - Rs 200
      etc.
      999.Done

3. Let the user select using the input method. Make sure the above said is in a loop. I prefer while loop.

4. Each time the user selects an item add it to an array. I recommend using just numbers as you already have food items on another array.
   eg:-

         int foodArr[200] = {2,5,9}
   

5. Then at the end of the ordering process when user hits that 999 or Done. Calculate the ordered food array and print it out.

Try this method and see. Else come back to us and someone else or me would be able to help you.

https://pastebin.com/TZNUsGSW