What should I do if I am unable to complete the revisions and write down the patent's voluntary revision of the specification to add a lot of content, but it does not exceed the original scope?

If you can’t write it down, write it in summary. Indicate: Supplement the technical solutions in the drawings attached to the manual into the manual.

Then submit a modification comparison page and mark all the modified parts so that the reviewer can see at a glance what you have changed.

I would like to remind you that there is no text description in the original manual. Although there is a text description in the attached picture, if you add a text description, the examiner will probably not accept it.