What will be happen to the size of string in this code?

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C

There are two strings in this code one is an array and another one is dynamically created using pointer.

1.If my input is less than 50 for string1 and less than 10 for string2 will the space that is not filled get wasted ,if so how to reduce the size.
2.In case of string 2 malloc size parameter is 10 and fgets size parameters is 10 what will happen if i increase the size to fgets(string2,50,stdin) which is greater than malloc size?
3.how to calculate the final size of input string in each case?I have used sizeof operator but it gave the hardcoded size that is 50 and 10 respectively for string1 and string2
4.Is there any other better approach to create a dynamic string?

What I have tried:

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int size=10;
    char string1[50];       
    char *string2;
    string2=(char *)malloc(size*sizeof(char));

    fgets(string1,10,stdin);
    printf("%s",string1);

    fgets(string2,10,stdin);
    printf("%s",string2);

}