if you r supposed to attend an audition of performances like rap or dance or rendition, You can say 저는 즉흥으로 하는 것은 잘 하지 못 하지만 최선을 다 해보겠습니다 , or 저는 프리스타일은 잘 하지 못 하지만 최선을 다 해보겠습니다 both sentences mean same, the upper one is accurate translation into Korean (for 'freestyling') , but they say 'freestyle' just same as 'freestyle' in english, even it's natural when it comes with hiphop or rap, if have further question, feel free to add, but plz let me know