Cost to t2rade buy or sell on Moomoo

Hello newbie question here but does it cost to buy or sell stocks here? New to the gamé a lot yt? o unravel I invested 50.00 initially in ....Sundial... went down like crazy....Today I tranferrd 20.00... now it says. net 20.52 net assets... security values 40.04.. cash -1952...could someone provide some Guidance what it means TY