How to safely change the site without losing positions in the search?

Question

Search Engine Optimization

(For example) there is a site www.kamp-eu.com . It is necessary to change the design, and, at best, rewrite or transfer to another engine.
What does it take to maintain positions in search engines?
Keep existing links? Save meta name="keywords" on pages with these links? (As far as I know Google ignores them). Save title?
The option that would give the most leeway would be to temporarily keep the old site open to search engines, and redirect users to the appropriate pages of the new one until search engine hits on the new links outnumber hits on the old ones. Of course, technically it can be gemorno, but interesting. But won't "Google ban"? Is it allowed to display other content to the user?

Answer 1

Keep existing links?
Save meta name="keywords" on pages with these links? (As far as I know Google ignores them)
Save the title?

Save everything.
You can get a ban, since one topic will be indicated, and users go to another site.