Issues in printing standing coin-like structure

[new3dprintinguser]

Hi, I am using Prusa i3 MK3 and PETG. Whenever I print structures with a standing coin-like end, I have two issues: 1. The lower half of the edge is not symmetrical to the upper half. i.e. While the upper half is circular, the lower half is not. It is like somebody ate a small piece of it. 2. The edge of the lower half that is on the support are rugged rather than smooth like the upper half. Is there any way that I can resolve these two issues?