The distance between buildplate and plastic nozzle tip is quite an important parameter affecting the quality of your prints. If it seems that plastic layers are too thin or too thick, nozzle tip scratches buildplate or previous layers or the quality of vertical walls of your model is insufficient due to improper plastic layup, try this procedure.
Press Maintenance > Calibrate > Z axis and follow the instructions. You will be asked to use a thin paper sheet to fine tune the gap between the nozzle tip and the buildplate.
Print any code to verify the results of the calibration, paying attention to brim and first layer layup.