Hello, I am trying to install the forum over https, but I don't get past step 2. I use https standard and the step 3 is being stopped because of the XMLHttpRequest cannot load due to access control checks. I am getting frustrated by this big time.

additional I get this:
Fatal error: Uncaught PDOException: SQLSTATE[HY000] [1698] Access denied for user 'root'@'localhost' in public_html/forum/sys/vendor/illuminate/database/Illuminate/Database/Connectors/Connector.php:47 Stack trace: #0 public_html/forum/sys/vendor/illuminate/database/Illuminate/Database/Connectors/Connector.php(47): PDO->__construct('mysql:host=loca...', 'root', 'root', Array) #1 public_html/forum/sys/vendor/illuminate/database/Illuminate/Database/Connectors/MySqlConnector.php(20): Illuminate\Database\Connectors\Connector->createConnection('mysql:host=loca...', Array, Array) #2 public_html/forum/sys/vendor/illuminate/database/Illuminate/Database/Connectors/ConnectionFactory.php(59): Illuminate\Database\Connectors\MySqlConnector->connect(Array) #3 public_html/forum/sys/vendor/illuminate/database/Illuminate/Database/Connectors/ConnectionFactory.php(47): Illuminate\Database\Connectors\ConnectionFactory->createSingleConnection(Array) #4 /U in public_html/forum/sys/vendor/illuminate/database/Illuminate/Database/Connectors/Connector.php on line 47

it seems it does not take the give login name and password set in step 2

Inform you about your hosting does have PDO enabled.

Make sure you have enabled SEF in sites/default/constants.php

Kind regards, Andy