RewriteEngine On
	
RewriteCond %(REQUEST_FILENAME) !-f
RewriteRule ^(.*[^/])$ /BG/$1/
	
RewriteCond %{REQUEST_URI} !/BG/css [NC]
RewriteRule ^(.*?)/(.*)/$ index.php?id=$1&sub=$2 [L]

Main Idea was that a request for /BG/something/more gets first converted to /BG/something/more/ and then to /BG/index.php?id=something&sub=more

However it sometimes either produces something along the lines of /BG/index.php?id=index.php

Any help is appreciated ^^