Table of Content didn't show up in wordpress and customization of a post

I am working on a wordpress post and I want to insert a table of content to the sidebar. Yet, I am not able to do so for unknown reason

I used the sidebar function to add the "table of contents", but it doesn't work. The table of contents doesn't show on the sidebar (see the picture below)

Another question is that I added the categories of the post to the menu. However, I found it not able to customize it with elementor ad it is not a page (see the picture below). Is there any way I can customize this page (for example add a background picture to the text "Core 1 opportunities and risks")?

Thank you very much for your help!