EDIT 2:
I have apllied fix only to the half of the model so I created version 3 with even smoother transition and appliied it on whole

EDIT:
I have printed it at 100% and 50% scale now it was mostly succes but overhang at the top was a bit to much and there were some strings showing so I have made it smaller and updated the model. It should be good now.
 
My first model like this. Can be used as a plant pot or a desk cup.