Composer

https://www.w3resource.com/php/composer/create-publish-and-use-your-first-composer-package.php

First check the version of composer if its intalled

composer -v;

Download the composer version like 

https://getcomposer.org/download/1.9.3/composer.phar)

Now in directory where composer.phar is located run

php composer.phar install

It will install composer.Thats it

Find all composer path

whereis composer

Downgrade the composer from 2 to 1

If you want to return to Composer 2 again.

Increase the Memory

set COMPOSER_MEMORY_LIMIT=99999999999&& php -d memory_limit=-1 composer.phar create-project –repository-url=https://repo.magento.com/ magento/project-community-edition magento2