Hey I tried to start the quest Fat Pirate Biggs but It just won't show up on the city board 

I should meet all conditions 

1. I already have married 10 girls 

2. I have Naomi and Shaana's CG scenes

     (solo and hot Spring)

Is there something I am missing??

Maybe you're missing a dialog/event with Shanna. Try to talk with her again, and then return to the city board. If that doesn't work, send me the save file to Naughty-Netherpunch@web.de and I'll check what the problem is.

Thx for the Tipp I did indeed miss a event with Shanna. It was the one with Ziki in the Forest behind Pumumu.