Geeetech

Hello everybody!
I have assembled my Prusa M201 quite quickly... but now I have still to have some result printing... Well, could be me doing something wrong... anyway, when I setup the height of the printing bed all the corners are at the same level but when checking the height at the centre of the bed, I find that the hotend touch the bed... like it's not flat! Well... any hint about?
Many thanks for all replies!

you may tighten the corner too much,so the center raised. loose them a bit and re-level it.

The aluminum plate is not flat enough, whatever the way the screws are tightened.
I solved this by adding a glass plate which is clamped other the aluminum plate.

Many thanks for your reply. I lowered the bolt that close the contact with the Z stopend and loosened a bit the screws of the bed... looks ok now!