What are the consequences of closing the site for maintenance?

Question

Angular

There is a site on a very dirty wp (in the code there are thousands of lines of unnecessary code from plugins that were once used). I want to install cms from scratch and return the content to my addresses. On terms - 3-6 days I plan.

After the work is completed, the page addresses will remain the same. The code will be reduced and the micro-markup will change significantly. New content will be added in a volume that is 4 times larger than the real one.

1. Is there any server response code or other methods that will tell Google that the site is under maintenance?
2. What kind of reaction can you expect from Google for this?
3. Is it worth adding content separately or is it better to do everything in one approach?

Answer 1

bower installed?
npm install -g bower

Answer 2

And now it doesn't work? Make edits locally, test to the maximum, then upload to a subdomain and check on the hosting. When everything is OK, then replace the main site. Downtime per hour will be with smoke breaks))

Answer 3

If the search bot does not crawl all the pages of the site or does not do it every minute, then such a fall out of the index may not affect at all.
But it's better to do it on a test domain)