Present a Google document and an audio file at the same time in Google Meet

The message is because the document has been placed in the owner's trash, and the trash has not been emptied yet. Once the trash is emptied it will not be available at all. How long that takes is individual. How often do you empty the "trash" on your desktop, for example?

To view the file you must, as Google instructed: * Sign in and make a copy, which will land in your documents, * Download the file to you computer (Google Docs Menu File -> Download), or * Contact the owner and request access.

Downloading does not require that you sign in. Then you can view/edit the file locally.

Note: Once the owner cleans out their trash, even that option will be gone.

From what I can gather, you are trying to create a system of internal links in a Google Doc. There are two effective ways to accomplish this.

One, take advantage of different headings from Format > Paragraph styles. You can modify the look and feel of these headings as you see fit. Then, when you highlight text to create a link, you will have the option of linking to the different headings you have created.

Two, create bookmarks within your document using Insert > Bookmark. This would be more suited to links that aren't headings but might be the start of a paragraph of something smaller that does not merit a heading. You can then create the link as with the previous option.

The design choice between the two is yours; you can mix and match them as well.