Redirect directory to new domain without touching the main site

Redirect directory to new domain without touching the main site

I would like to redirect https://mineyourmind.de/forum to
https://mineyourmind.net/forum .
Every rewrite rule I could google didn´t work, they also redirected the
main domain (mineyourmind.de).
Im redirecting http:// www. and http:// and https:// via the apache
siteconfig.
RewriteEngine On
RewriteCond %{HTTPS} off [OR]
RewriteCond %{HTTP_HOST} ^www\.mineoyurmind\.de$ [NC]
RewriteRule (.*) https://mienoyurmind.de%{REQUEST_URI} [R=301,L]
The .htaccess of the forum directory looks like this:
ErrorDocument 401 default
ErrorDocument 403 default
ErrorDocument 404 default
ErrorDocument 500 default
<IfModule mod_rewrite.c>
RewriteEngine On
# If you are having problems with the rewrite rules, remove the "#"
from the
# line that begins "RewriteBase" below. You will also have to change
the path
# of the rewrite to reflect the path to your XenForo installation.
#RewriteBase /xenforo
# This line may be needed to enable WebDAV editing with PHP as a CGI.
#RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -l [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^.*$ - [NC,L]
RewriteRule
^(data/|js/|styles/|install/|favicon\.ico|crossdomain\.xml|robots\.txt)
- [NC,L]
RewriteRule ^.*$ index.php [NC,L]
</IfModule>
Should I add the rewrite for mineyourmind.de/forum to
mineyourmind.net/forum to the apache site config or to the htaccess and
how should this look like ?