Do you like Taekwondo?

PHP, 241 bytes

<?=preg_replace(["#\b(President|Founder)\b#i","#\bMaster instructor\b#i","#\bTeacher\b#i","#\bBlack Belt\b#i","#\b(Studen|Color Bel)t\b#i","#\bMaster level\b#i"],[Gwanjang.$n=" nim",Sabeom.$n,Gyosa.$n,Dan,Geup,Godanja],"$argn, *side-kick*");

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C#, 262 bytes

s=>{for(int i=0;i<8;)s=s.ToUpper().Replace("PRESIDENT|FOUNDER|MASTER INSTRUCTOR|TEACHER|BLACK BELT|MASTER LEVEL|STUDENT|COLOR BELT".Split('|')[i],(i<2?"GWANJANG":i>3?"GEUP":"SABEOM|GYOSA|DAN|GODANJA".Split('|')[i-2])+(i++<4?" NIM":""));return s+", *SIDE KICK*";}

Full/Formatted version:

class Program
{
    static void Main(string[] args)
    {
        System.Func<string, string> f = s =>
        {
            for (int i = 0; i < 8;)
                s = s.ToUpper().Replace("PRESIDENT|FOUNDER|MASTER INSTRUCTOR|TEACHER|BLACK BELT|MASTER LEVEL|STUDENT|COLOR BELT".Split('|')[i],
                                        (i < 2 ? "GWANJANG"
                                               : i > 3 ? "GEUP"
                                                       : "SABEOM|GYOSA|DAN|GODANJA".Split('|')[i-2])
                                        + (i++ < 4 ? " NIM" : ""));

            return s + ", *SIDE KICK*";
        };

        System.Console.WriteLine(f("I am a Student and I do Taekwondo twice a week"));
        System.Console.WriteLine(f("I am a Teacher willing to be a President"));

        System.Console.ReadLine();
    }
}

Retina, 154 bytes

i(`president|founder
Gwanjang_
master instructor
Sabeom_
teacher
Gyosa_
black belt
Dan
student|color belt
Geup
master level
Godanja
_
 nim
$
, *side kick*

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