Page Must Not Already Have A Parent Error (Navigation Page)

Hi everyone, i have a navigation page on my app as a tab of a TabbedPage. In the root page i have a button which has pushasync function to push the next page. I can navigate with this button and then come back with the Back Button of the NavPage. But If I press the tab icon of my Navigation Page on my Tabbed Page, it goes to the root page. Then if i press my "button" (pushasync), i get an error. It says, Page must not already have a parent..

Please help me!