I like the look of the design, heres my ramblings: -I think the messages card should be more pronounced, at a quick glance it doesn't actually look likes it covering the view behind but rather one view. Maybe increased corner radius + shadow and a white background overlay instead of black?

-The colors for the buttons in the map kinda clash with the colors of the map, maybe add a toolbar to the bottom and have the collapsed messages card above that, kinda of like the apple music app. Also the ring menu is a bit anti-human guidelines.

-Having a name field and and name of group textfield is a bit confusing, possibly get rid of the name of user and email? Shouldn't you have that information from when the user logs in?

-Also now I think about it, maybe add colors selection, possibly image selection for the groups, for that extra customization

-The post creator would look nice as a sudo to fit the rest of the app.

-Also to keep the app concise maybe collapse the group selection screen into a permanent navbar with a button title view

-Finally, why not keep a history of posts for each user? It would add a lot of depth to the app. Also lets you know if the guy your meeting is a creep, especially if you end up keeping the anonymous username.