set in "Extruder " Extrusion witdth to "manual" and set it to 0.8 mm (Its line width, but line is in s3d called extrusion )
in "Layer" set layer height to 0.3mm
check your model for errors with meshmixer or windows-APP "3D-Builder", they have good repair-capabilities play with settings under Advanced -> "External Thin Wall Type" and "INternal Thin Wall Type" and set it to single extrusion walls vary the number of Outline/Perime...