For sure your Z-Gap is not good.
First you have to clean the extruder.
Go to PJ-Con set the temperature to 180°C and when the head becomes hot remove clean it.
Exit from PJ-Con and while the extruder is cooling continue to clean it because some plastic can come out from the nozzle.
Before setting the Z-Gap check the noozles they must be clean or you'll not be able to set the right z-gap.
Go into the printer menu and check the level of the bed, if needed adjust it with the screws according to the Cubex Manual.
Now go to Z-Gap and with the arrow place the bed very close to the extruder, you should have less than the height of a paper sheet, check with a light to see how you are close, but the nozzle doesn't have to touch the bed.
Save your settings.
Repeat the Z-Gap to check if it's good, if not correct and check again.
Having the Level and the Z-Gap set with precision is the first step to have a good print, it they are good you'll see at the beginning of the print that the skirt is a little squished on the bed like here :