When your printer has to make layers that go beyond the previous layer, it is called an "overhang". If your printer does not have sufficient cooling on the model, the section has difficulty staying in the air as the soft plastic must struggle with gravity. The faster the plastic hardens, the better it will look on the underside. These are some tricks for how to achieve better results on overhangs.
Support is a kind of scaffolding that helps the printer build the model in places that would otherwise be challenging or impossible. Support is built together with the model and is made to be easily removed and thrown out when the print is finished. The slicer automatically generates it under surfaces on your model, where the angle exceeds about 45 degrees. Support is enabled in the settings of your slicer.
Print a little cooler
By lowering the print temperature you can shorten the time that elapses from the plastic leaves the nozzle till it solidifies. Try lowering the temperature by 10 degrees (but no lower than 190 degrees, or whatever the minimum temperature is for your filament) and see if that solves the problem. This can help with the sagging of the lines but can in turn result in under extrusion, so be aware of that.
Lack of proper cooling of the part while it is printing is often the reason why your print ends up as in the picture. Turn on the fan from your control panel, check if your fan is running as it should and feel under the nozzle (while it is cold) if it is working properly. If not, you can check the wires and see if they are damaged or you can just replaced the fan with a new one.
There are a lot of printers that come with only one fan to cool the part. In many cases this is perfectly fine but it can happen that the print itself can block the air from reaching the point to be cooled. A lot of people design parts that are ready to be printed and replaced with the existing parts. They can help redirect the air around to the other side of the nozzle and cover more of the model. Models deisgned specificly for your printer can often be found on sites like Thingiverse and MyMiniFactory.
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