Can't read null terminated string from binary file in C

I have a which is launched in repl.it. The problem is that is doesn't properly reads null-terminated string from the file:

x == 228
y == Hell
x == 228
y ==  @

The last line should be y == Hell. How to fix my code?

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

struct A {
  int x;
  char *y;
};

#define INITIAL_BUFFER_LENGTH 10

char *read_string_from_file(FILE *handle) {
  int string_capacity = 10;
  char *string = malloc(string_capacity);
  int count = 0;
  char c;
  while ((c = fgetc(handle)) != '\0') {
    string[count] = c;
    count++;
    if (count == string_capacity) {
      string_capacity *= 2;
      string = realloc(string, string_capacity);
    }
  }
  string[count] = '\0';
  return string;
}

int main(void) {
  struct A *obj = (struct A *)malloc(sizeof(struct A));
  obj->x = 228;
  obj->y = "Hell";
  printf("x == %i\n", obj->x);
  printf("y == %s\n", obj->y);

  FILE *file = fopen("f.txt", "w");
  fwrite(&obj->x, sizeof(obj->x), 1, file);
  fwrite(&obj->y, strlen(obj->y) + 1, 1, file);
  fclose(file);

  obj->x = 0;
  obj->y = NULL;

  file = fopen("f.txt", "r");
  fread(&obj->x, sizeof(obj->x), 1, file);
  obj->y = read_string_from_file(file);

  printf("x == %i\n", obj->x); // must be 228
  printf("y == %s\n", obj->y); // must be Hell
  return 0;
}