For the first issue, I guess you didn’t sticked that to bottom. Currently if you scroll the screen you should see the tab bar so set the fix type as bottom. Is this app is a responsiveness app or a legacy app?
For the second issue, is that a modal screen and does the button link action type is modal?
I am trying to make a mobile app. Now when I preview and scroll I see the app bar, obviously this is not what happens to an app bar on an app. How do I fix? are the screens too long?