Don't want to sound mean ok? but you got the wrong size... the 52 is 537mm effective top tube... you need at least the next size that is 548mm effective top tube. I dare to say that you are between sizes... because the next bigger 565mm could work as well.

You can make it work but you might need at least a 12 cm stem (IMO 13), all the seat back you could get and flip the stem (not looking up), do not slam the stem.

Just being honest with you, sure the seller told you that was fine too... if it helps you got a good deal in the bike.