D8 Acquia on external drive Mac

Hi.

I have D8 on an external hard drive. Everything works... almost.

— 1. —

I have .../sites/default AND .../sites/sitename.dd twice (with all the files duplicated). Can I delete one of the duplicates?

— 2. —

When updating from 8.1.8 to 8.1.9, I get this message : Your sites/sitename.dd/settings.php file must define the $config_directories variable as an array containing the names of directories in which configuration files can be found. It must contain a sync key."

I tried to put in one of the settings.php : " $config_directories['sync'] = 'config_hash'; " But Drupal told me that such file did not exist.

The hash came from a file name containing 2 folders ("staging" and "active"). I'm missing something, but I cannot see what.

Thanks for helping.

Anne.