Go to your terminal. You can find it at my.world4you.com under Your package > Webspace > Terminal after you have clicked Install Terminal. Then download composer using the following command:
curl -LO https://getcomposer.org/composer.phar
You can then use the ls command to verify that composer was downloaded correctly.
composer can now be used with the following command:
COMPOSER_HOME=~/.composer php72 composer.phar -n
php72 stands for your PHP version, in this case PHP 7.2. If you are using a different version of PHP, adjust the command accordingly, e.g. php71 for PHP version 7.1. The -n parameter is used because the terminal does not allow currently running programs.
Please note that composer commands can take longer and the terminal will not respond during load time. It is therefore advisable to wait a little bit after each step.
To delete composer, all you need to do is remove the composer.phar file in your directory. The cache files of composer are stored in the webroot directory under .composer and can also be deleted in this case.