Installing Drupal

OK, I'm a bit confused; I'll apologize if necessary, as this isnt necessarily a DRUPAL Installation question, but it is Drupal related, and IS an Installation question, so...

I'm attempting to install Drush. As I've looked at Google, I'm seeing some places that tell me to Install Composer, and then use Composer to install Drush; while other places are saying to install Drush first, and then use Drush to install Composer... OR Does it matter which is first?

Error -- Cannot serve directory -- using composer "drupal-project", did i mess scaffolding up, or something more basic?

Can someone point me in right direction for use of Composer creating a multi-site configuration? I'm using the composer project : "drupal-composer/drupal-project".

I'm not sure if I've messed up the scaffolding setup or overlooked something else more trivial. Have spent 8-10 hours googling similar threads and trying to figure it out without success. Can someone point me in right direction?

Can someone point me in right direction for use of Composer creating a multi-site configuration? I'm using the composer project : "drupal-composer/drupal-project".

I'm not sure if I've messed up the scaffolding setup or overlooked something else more trivial. Have spent 8-10 hours googling similar threads and trying to figure it out without success. Can someone point me in right direction?

Configured s/w is: Ubuntu 16.04/Apache 2.4.18/MariaDB 15.1 (10.0.28-MariaDB)/PHP7.0.8ubuntu0.16.04.3.

I'm facing problem on local versions of drupal that i've downloaded through git clone
However, I have two other drupal installations working perfectly(8.0.x via clone and 8.3.x-dev via .tar.gz)
git clone --branch 8.3.x https://git.drupal.org/project/drupal.git drupal83

I've cloned 8.3.x and 8.2.x using the above command and both of them return the same "HTTP ERROR 500".
On checking the apache log it says about some problems in including "autoload.php" as in the following lines

I am very new to Drupal and having to pick it up quickly here at work. I have a problem that I've been stuck on for half a day.

My question is: When you click on a course page and look at the block "at a glance", there are stakeholders at the bottom of that block that were inserted when creating the block. Once a specific stakeholder group in the "at a glance" box section has been tagged, the course should show up on that stakeholders page.2 of my courses are not showing up and 2 of them are.

I just started working on drupal 8.2.4 and setup first drupal 8 project "drupal8_1" in my www folder and it was working fine with url http://localhost/drupal8_1. Then I installed another drupal 8 project "drupal8_2" in www folder.