Multisite gives Error if i want to enter Dashboard or Site

I´m struggling for 3 days now. I want to create a WordPress Multisite System with subdirectories. As Server im using Apache.
My wordpress is installed at /var/www/html/wordpress
In order to do so i followed the installation instruction and added to my wp-config.php

define('MULTISITE', true);
define('SUBDOMAIN_INSTALL', false);
define('DOMAIN_CURRENT_SITE', 'myadress');
define('PATH_CURRENT_SITE', '/wordpress/');
define('SITE_ID_CURRENT_SITE', 1);
define('BLOG_ID_CURRENT_SITE', 1);

After this i change my .htaccess file to

RewriteEngine On
RewriteBase /wordpress/
RewriteRule ^index.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*.php)$ $2 [L]
RewriteRule . index.php [L]

Now i want to add a new page for this i click on the menu to add a new site. After adding if i want to go to the dashboard. But i always get an Error that says that the requested URL was not found on the Server.
I also enabled apache mod_rewrite.
As solution to show 2 websites i now created a subdirectory and installed a new version of wordpress there. Now i can see the second the dashboard and the site. But this is a new Instance or ? Because if i am in the Dashboard of the subdirectory i cant go back to the parent multisite dashboarf.
Has anybody an idea why that is the case ? I’m new to WordPress and can’t find the Solution.

Thanks for your Help

Moe