Hyundai Tiburon Gk 2.0 gls eats the oil

Hello dear forum! Have a strange problem and I’ll ask myself in a forum. Google meant with you I’m right. So. I bought me a Hyundai Tiburon Gk 2.0 gls year 2005 with 200,000 km. Engine runs quietly and he does not install any other. ONLY he eats the oil away from me! I filled in 4 1/2 liters of oil on 300 km! But he doesn’t burn it! Also he doesn’t lose oil! It’s just gone. o.O. According to the seller, the cylinder head gasket has been filled with 4 1/2 liters of oil! The mechanic that did this then filled up to max. and it ran perfectly. My guess was that he had too little oil in the tub, but would it have to be already full or?! Does anyone have any idea what could be there? Since he is already dry again, I am filled up with dust again when I think of him, but I’m afraid that he might drown in the oil. xD I thank you already now for your Antw Detection!