If you can not login to your wordpress site using administrator account in conventional methos, then you may create another administrator account using mysql commands.
Complete guide to host multiple WordPress sites in a LEMP stack in a Ubuntu 16.04 LTS. Installation of SSL by Let’s Encrypt has been illustrated also.
To remove website field from comments and user profiles in a wordpress powered site you need to run the few mysql commands in the terminal window of VPS.
How to host multiple websites in a Linode on Debian linux distribution, Nginx as web server, MySQL as database, PHP5-FPM as language processing from Windows PC.
You need to copy olddb.sql file to your new host. You may use FTP programme to download the SQL file from old host and then upload to the new host.