Make visual adjustments all across the apps for a better look and feel.
Delete double Appbars. At most one appbar should be visible at any time.
Adjust bottom navigation bar to not be at the absolute bottom. Add a bit of a padding to the bottom so that the items are more visible, especially in iOS.
Make the sign up button bigger. In its current form, it is too small for it to be seen easily. It should be easily noticeable for the user.
Make visual adjustments all across the apps for a better look and feel.