UISearchController search bar overlap first cell when active

I am using UISearchController to search for data in my tableview. I am not using table view controller. I would like to hide the navigation bar when my search bar is active therefore I set self.searchController.hidesNavigationBarDuringPresentation = YES; to yes.

However when I do this and want to search, my active search bar covers part of the first cell. the covered part has same height as status bar.

I tried other articles and questions similar to this one but nothing helped me to solve it. Then I started to play with the table view header size. I did this

 -(CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section{

  return 20.0f;
}

The result was that when I tapped search bar an started to search problem was not there anymore.

However when the search bar is not active there was a gab between searchbar and first cell

Any ideas how to fix this issue?

Edit: after adding self.automaticallyAdjustsScrollViewInsets = false;