Need Some Help Adding Some Features I Just Started Doing Programming In My Class

#include <stdio.h>
#include <conio.h>

int main(){
//totalbilling ang quantity are variables for the case study 1
	float tuifee, totalfee, disinte, totalbilling;
	int mode, quantity;
//to get tuition fee
	printf("\n 1 Burger             Php10.50\n");
   printf("\n 2 Foot Long          Php36.75\n");
   printf("\n 3 Shawarma           Php62.50\n");
   printf("\n 4 Fries              Php25.60\n");
   printf("\n 5 juice              Php10.00\n");
   printf("\n 6 Shake              Php15.00\n");
   printf("\n 7 Press Exit");
   printf("Select 1,2,3,4,5,6,7-->");

//display menu

//get the user's choice
	printf("\n\nEnter your order: ");
	scanf("%i", &mode);


switch(mode){
//case 1 is the actual computation when you order burger (just change the price if necessary)
//This case 1 code applies to all cases just change the price depending on the price given per item
	case 1:

        printf("How many Burger you want to order: ");
        scanf("%i", &quantity);
        totalbilling=totalbilling+(10.50*quantity);
        if(totalbilling<=20)
        {

         printf("Total: %.2f", totalbilling);
         }
        else if(totalbilling > 20);
        {
         printf("wrong inpute");
        }
        break;

	case 2:

        printf("How many Foot Long you want to order: ");
        scanf("%i", &quantity);
        totalbilling=totalbilling+(36.75*quantity);
        printf("Total: %.2f", totalbilling);
		  break;
	case 3:
		  printf("How many Shawarma you want to order: ");
        scanf("%i", &quantity);
        totalbilling=totalbilling+(62.50*quantity);
        printf("Total: %.2f", totalbilling);
		  break;
	case 4:

        printf("How many Fries you want to order: ");
        scanf("%i", &quantity);
        totalbilling=totalbilling+(25.60*quantity);
        printf("Total: %.2f", totalbilling);
      break;
   case 5:

        printf("How many Juice you want to order: ");
        scanf("%i", &quantity);
        totalbilling=totalbilling+(10.00*quantity);
        printf("Total: %.2f", totalbilling);
        break;

   case 6:

   	  printf("How many Shake you want to order: ");
        scanf("%i", &quantity);
        totalbilling=totalbilling+(15.00*quantity);
        printf("Total: %.2f", totalbilling);
        break;

   case 7:

		getch();
		break;
		default:
		printf("wrong input");
}
getch();
}