How does mysql_real_escape_string() work?

Question

I have to send some string (in C) as a query to MySQL, so i used mysql_real_escape_string() to escape some characters like \0 or \n:

#include <mysql/mysql.h>
int loginQuery(char *Nickname, char *Password)
{

    char bufferutility[READBUFSIZE]="SELECT * FROM user WHERE Nickname='";
    char bufferutility2[READBUFSIZE*2+1];
 
    strcat(bufferutility,Nickname);
    strcat(bufferutility,"' AND Password='");
    strcat(bufferutility,Password);
    strcat(bufferutility,"';");
  
    if(mysql_real_escape_string(conn,bufferutility2,bufferutility,strlen(bufferutility))==(unsigned long)-1){
        printf("\nEscaping error\n");
    }
 
    //code for mysql_real_query() here  
}

But I got this error:

You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near ''Hello\n' AND Password='World\n'' at line 1

What have I done wrong?