Step-by-step for Elgg 3

Console commands (by root aka sudo) to setup all requirements to install and use Elgg (Ubuntu/Debian OS):

apt-get update && apt-get upgrade

apt-get install mysql-server

How To Install MySQL

apt-get install nginx

How To Install Nginx

apt-get install php-pear php7.4 php7.4-fpm php7.4-zip php7.4-curl php7.4-gd php7.4-mysql php7.4-xml php7.4-mbstring php7.4-xsl php7.4-intl php7.4-cgi php7.4-cli php7.4-common php7.4-readline php7.4-imagick php7.4-opcache php7.4-sqlite3 php7.4-gmp

How To Install PHP 7.4

You can now work with this environment.

Easiest way is to use Docker (if you know what this means).

Look at these solutions:

https://github.com/ColdTrick/elgg_webserver

https://github.com/mrclay/elgg-docker

https://github.com/mrclay/elgg-docker-2

https://github.com/demyxco/elgg

I really thank you
Are there Docker tutorials

Well, after I take these steps,
Can I copy my website files?
Database
And do a recovery on the new server?

These steps are prerequisite.

You must complete them before you can migrate your data and install Elgg.

Follow https://learn.elgg.org/en/stable/admin/duplicate-installation.html

Don't forget about backup !

Nikolai Shcherbin