System administrator WordPress

Hello, I have a WordPress website (online news magazine), and the site is facing some difficulties. We think it is a database problems (php), besides being with the outdated version the memory management is not working properly so it crashes. We built a new site and an attempt was made to make a site migration, but it was not possible to do so, so a copy was made and a redirect was attempted. Now the other databases (mail contacts and notifications) don't work because they don't recognize the redirect. Old facebook posts don't recognize it either, and if we publish with the old site, it clashes with the new one. It is our understanding that only a system manager will be able to solve the problem to "cure" the database and correct the redirects (wrong or not). We need to migrate our new site to the old with all the contacts, notifications etc. Do you think Looking forward to hearing from you..