RewriteRule won´t work with new domain - .htaccess

Question

I´ve made some RewriteRules in my .htaccess and they all work if I call my Website from the Domain/URL of my server.
Now I wanted to point an external Domain to my subfolder on my server where my Website is located, but all RewriteRules aren´t working anymore. When I call the php-files everything is alright, but when I call my "beautiful" links, I wanted to create, then only error 404 is shown.
This is currently my .htaccess file:
ErrorDocument 401 /401.php
ErrorDocument 404 /404.php
RewriteEngine On
#redirect www request to the base domain
RewriteCond %{HTTP_HOST} ^www\.(.+)$ [NC]
#RewriteRule ^(.*)$ http://%1/$1 [R=301,L]
#ignore existing files and directories
RewriteCond %{REQUEST_FILENAME} -f [NC,OR]
RewriteCond %{REQUEST_FILENAME} -d [NC]
RewriteRule .* - [L]
# Check if query string exists
RewriteCond %{QUERY_STRING} ^$
# Check that the request is not for an existing file
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^spielplan$ spielplan.php [NC,L]
RewriteRule ^rangliste$ rangliste.php [NC,L]
RewriteRule ^alletipps$ allbets.php [NC,L]
RewriteRule ^benutzerseite$ userpage.php [NC,L]
RewriteRule ^einstellungen$ usersettings.php [NC,L]
RewriteRule ^spiel/([0-9]+)/?$ spiel.php?id=$1 [NC,L]
RewriteRule ^user/([A-Za-z0-9-]+)/?$ user.php?name=$1 [NC,L]
RewriteRule ^([A-Za-z0-9-]+)/?$ $1.php [NC,L]

Answer 1

I found a solution.
Because I tried to map my domain to a subfolder, this subfolder needs to work like an DocumentRoot and not like a subfolder.
So I needed to add:
RewriteBase /
in my .htaccess