RewriteEngine On

RewriteCond %{HTTP_HOST} !^www.wellness.ost-see-urlaub.de$ [NC]
RewriteRule ^(.*)$ https://www.wellness.ost-see-urlaub.de/$1 [L,R=301]
RewriteCond %{SERVER_PORT} !^443$
RewriteRule (.*) https://%{HTTP_HOST}/$1 [R=301,L]
RewriteCond %{REQUEST_URI} ^/index.php(/.*) [NC]
RewriteRule ^(.*) %1%2 [R=301,L]

ErrorDocument 404 https://www.ost-see-urlaub.de/errors/notfound.htm
ErrorDocument 402 https://www.ost-see-urlaub.de/errors/notfound.htm
ErrorDocument 403 https://www.ost-see-urlaub.de/errors/notfound.htm
ErrorDocument 404 https://www.ost-see-urlaub.de/errors/notfound.htm