What to consider in SEO when changing one site to another?

Question

Search Engine Optimization

There is an old (current) site on the main house.
We made a new site with new content (a well-thought-out decision already!)

- We are going to transfer the old (current) site to the old subdomain
- And put the new one on the main domain

What is good to foresee (do) in terms of SEO?

Answer 1

What is good to foresee (do) in terms of SEO?

In terms of SEO, it is better to remove the old site. If all this belongs to one organization, then there will be gluing and duplicates. Just replace the old one with the new one according to all the rules.

Answer 2

Save all SEO content and old URLs, close the old site with authorization from robots