error with a Query mercury

Hello i Have a error with a query in Mercury

Code:

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queryreactor2.runFastQuery("INSERT INTO verwarnungen (username, grund, massnahme) " + "VALUES (" + this.GetHabbo().Username + ",unnoetig, wtf);");

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the errorlog Say:

Code:

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INSERT INTO verwarnungen (username, grund, massnahme) VALUES (Crysas,werben, lol);
MySql.Data.MySqlClient.MySqlException (0x80004005): Unknown column 'Crysas' in 'field list'

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Crysas is my Username?