int main() {
    errno = 0;
    const char *filename = "/Users/davidfrenzel/Google Drive/Studium/Semester 1/Programmierung 1/Projects/Uebung4/...";

    FILE *file;
    file = fopen(filename, "r");

    if (file == NULL) {
        fprintf(stderr, "%s\n", strerror(errno));
        exit(1);
    } else{
        printf("The file %s was Found\n", filename);
    }
    return 0;
}

No such file or directory
(You're right!)

BUT:
int main() {
    errno = 0;
    const char *filename = "...";

    FILE *file;
    file = fopen(filename, "r");

    if (file == NULL) {
        fprintf(stderr, "%s\n", strerror(errno));
        exit(1);
    } else{
        printf("The file %s was Found\n", filename);
    }
    return 0;
}

The file ... was Found

change the code to:
int main() {
    errno = 0;
    const char *filename = "...";

    FILE *file;
    file = fopen(filename, "r");

    if (file == NULL || filename == "...") {
        fprintf(stderr, "%s\n", strerror(errno));
        exit(1);
    } else{
        printf("The file %s was Found\n", filename);
    }
    return 0;
}

Of course errno won't be set to anything but that way I could tell the programm to return an error (in the function seen in question) if the filename == "...". Kind of as a workaround I guess