////////////////////
STEP 1:Get Composer.
------------
run all commands one by one
------------
1.)

php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"

2.)

php -r "if (hash_file('SHA384', 'composer-setup.php') === '544e09ee996cdf60ece3804abc52599c22b1f40f4323403c44d44fdfdd586475ca9813a858088ffbc1f233e9b180f061') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;"

3.)

php composer-setup.php

4.)

php -r "unlink('composer-setup.php');"

Install Slim:
------------
1.)

php composer.phar create-project slim/slim-skeleton MySlimProject02

(give it time...reach up to "Generating autoload files").
Wait for new command line.
Set the version.(make sure which version you want/need(optional)).

****drag composer.phar into "MySlimProject02"
***run gitbash in "MySlimProject02"
***continue step 2
2.)

php composer.phar require slim/slim "^3.9.1"

Install Twig:
-------------
1.)

composer.phar require "twig/twig:^2.0"