Incorrect SSL-configuration for BookStack - apache

Question

after trying unsuccessfully to set up BookStack with nginx, I switched to Apache.
However, I have similar difficulties setting up the subfolder.
BookStack should be available at https://domain.name/bookstack.
The location of BookStack is /var/www/bookstack/... .
I have also added the domain in the .env.
I just figured out, that the configuration for HTTP works like expected.
<VirtualHost *:80>
ServerName domain.name
ServerAdmin webmaster#localhost
DocumentRoot /var/www/html
ErrorLog ${APACHE_LOG_DIR}/error.log
CustomLog ${APACHE_LOG_DIR}/access.log combined
# BookStack Configuration
Alias "/bookstack" "/var/www/bookstack/public"
<Directory "/var/www/bookstack/public">
Options FollowSymlinks
AllowOverride none
Require all granted
RewriteEngine On
# Redirect Trailing Slashes If Not A Folder...
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)/$ /$1 [L,R=301]
# Handle Front Controller...
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^ index.php [L]
</Directory>
<Directory "/var/www/bookstack">
AllowOverride None
Require all denied
</Directory>
# End BookStack Configuration
</VirtualHost>
But when I put in the config for HTTPS (I created a certificate with certbot/letsencrypt), I get the login page without styles. As I log in, it takes me to HTTP-domain with error 404 Not found.
Here's my current SSL config:
<IfModule mod_ssl.c>
<VirtualHost *:443>
ServerName domainname
ServerAdmin webmaster#localhost
DocumentRoot /var/www/html
ErrorLog ${APACHE_LOG_DIR}/error.log
CustomLog ${APACHE_LOG_DIR}/access.log combined
# BookStack Configuration
Alias "/bookstack" "/var/www/bookstack/public"
<Directory "/var/www/bookstack/public">
Options FollowSymlinks
AllowOverride none
Require all granted
RewriteEngine On
# Redirect Trailing Slashes If Not A Folder...
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)/$ /$1 [L,R=301]
# Handle Front Controller...
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^ index.php [L]
</Directory>
<Directory "/var/www/bookstack">
AllowOverride None
Require all denied
</Directory>
# End BookStack Configuration
SSLEngine on
SSLCertificateFile /path/to/certificate/file
SSLCertificateKeyFile /path/to/certificate/key/file
Include /etc/letsencrypt/options-ssl-apache.conf
</VirtualHost>
</IfModule>
# vim: syntax=apache ts=4 sw=4 sts=4 sr noet
I don't get the problem with this.