I created a table of contents with multilevel headings for my document and it is almost perfect. However, heading 11.1 and 11.2 appear under heading 10 instead of heading 11. Any idea what I might have missed? Greatful for your support.
This could relate to how the document was constructed. Is the text one continuous flow or broken up into separate text frames?
It's different text frames, but I think they are created in the correct order. If not, how can I change the order?
Normally text you be in a direct flow with threaded text frames, but better in a single frame. You can link texts later together, if not done before: add at the final text a return (it might cause overflow warning, but here you should ignore it). Where the overflow +-symbol is, click once and then click in the next frame.
But for the future, work with the keep options in paragraph styles and space before and after. Avoid making to many frames, as it often causes a mess and if you have to make changes in the document you have a bunch of additional work. This shall be avoided.
Using threaded frames eliminates this from happening.
If you need to use unthreaded frames, usually moving the title frames (1., 2., 11., etc.) further to the left—and adding an indent so that the text lines back up with the text underneath—takes care of it.