Simply tell him to stop flirting with you. If he’s too stupid to understand that you don’t want to be flirted with , tell him “ I want you to be more formal/professional with me “ or that kind of statement. No please , no I would aprreciate if ... (coming from a guy). Geez , I’m not blaming you but you’re 19 already . If he’s a sound person , he would understand . If he’s too dumb , he’ll make your job hell and maybe force you into quitting ( if he fires you for no valid reason , boy can court fuckim up) . Do you see that , very simple . This “ I’m not a confrontational person” is so full of childish shit . Don’t let him touch you , and firmly reject his “ flirting” . Okay ?