Child theme messes up main menu in Twentyeleven theme

I’m new to wordpress and am trying to customise the Twentyeleven theme.

I have read many posts advising that customisation to the Twentyeleven theme is best done with a child theme. I followed the instruction on https://codex.www.ads-software.com/Child_Themes and set up and activated an “empty” child theme with a style.css containing the following code:

‘/*
Theme Name: Twentyeleven Child
Description: Child theme for the twentyeleven theme
Author: Raymond Mah
Template: twentyeleven
*/
@import url(“../twentyeleven/style.css”);’

However, this empty child theme css messes up the main menu in my Twentyeleven theme. What happened is that my menu items got re-arranged and sub-menu items got moved up to the main menu. The menu no longer follows the ordering set in the Appearance>Menus page.

I can fix the sub-menu problem by using the Page Attributes option for each page. However, what I cannot fix is:
(1) the menus are now appearing in alphabetical order instead or in the order set in the Appearance>Menus page; and
(2) a page that has (no parent) now appears in my main menu even though it is not set to appear on the main menu in the Appearance>Menus page.

It essentially seems that the empty child theme completely removes the effect of the settings in the Appearance>Menus page.

I would appreciate any advise on how to fix this. Thanks!

Regards,
Raymond