The problem is that in Luban there is no way currently to let the slicer know you are using a different sized nozzle (0.4mm standard). Because of this the printer is extruding a volume of plastic that is 4x greater than it should be (area of circle with 0.2mm diameter is 1/4 that of a circle with 0.4mm diameter). It is also slicing the model with the assumption that your walls are 0.4mm thick, this will result in walls not contacting and supporting each other properly.
With so much extra plastic being extruded and unsupported walls it is not surprising that overhangs & bridges droop massively.
What you calibrated was the amount of plastic being driven/fed by the extruder gear into the hot end, the second step to calibrating your extrusion is to print a hollow box with one wall thickness and measure the thickness of your walls to confirm the correct amount is being extruded out of the nozzle.
Take a look at this thread to understand extruder calibration better:
You will need to start using a different slicer such as Cura, Slic3r etc. to allow for different nozzle sizes.