Where i must insert this 3 Lines in my htaccess....

RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www\.)?somedomainname\.ch(/.*)?$ [NC]
RewriteRule \.(bin|rar|zip|exe|ipsw|gif|jpg|GIF|JPG|jpeg|JPEG)$ http://www.somedomainname.ch/assets/sorry.gif [R,L]

At the moment they are at this position. But they do not work.
I would only protect all my Files from Hotlinking.

### SILVERSTRIPE START ###
<Files *.ss>
Order deny,allow
Deny from all
Allow from 127.0.0.1
</Files>

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /

# RewriteCond %{HTTP_HOST} ^somedomainname\.ch [nc]
# RewriteRule (.*) http://www.somedomainname.ch/$1 [R=301,L]

RewriteCond %{REQUEST_URI} !(\.gif)|(\.jpg)|(\.png)|(\.css)|(\.js)|(\.php)$

RewriteCond %{REQUEST_URI} ^(.*)$
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule .* sapphire/main.php?url=%1&%{QUERY_STRING} [L]
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www\.)?somedomainname\.ch(/.*)?$ [NC]
RewriteRule \.(bin|rar|zip|exe|ipsw|gif|jpg|GIF|JPG|jpeg|JPEG)$ http://www.somedomainname.ch/assets/sorry.gif [R,L]
</IfModule>
### SILVERSTRIPE END ###

I would be very happy if some one can help me... because my Servertraffic is about 10GB /day only trought Hotlinking. ;-(

You should place your rewrite rule above the SilverStripe rules, since these will match first and then your rule won't be executed at all.
Your file should look like this:

### SILVERSTRIPE START ###
<Files *.ss>
Order deny,allow
Deny from all
Allow from 127.0.0.1
</Files>

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /

RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www\.)?somedomainname\.ch(/.*)?$ [NC]
RewriteRule \.(bin|rar|zip|exe|ipsw|gif|jpg|jpeg)$ http://www.somedomainname.ch/assets/sorry.gif [NC,R,L]

RewriteCond %{REQUEST_URI} !(\.gif)|(\.jpg)|(\.png)|(\.css)|(\.js)|(\.php)$

RewriteCond %{REQUEST_URI} ^(.*)$
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule .* sapphire/main.php?url=%1&%{QUERY_STRING} [L]
</IfModule>
### SILVERSTRIPE END ###

You can also remove the uppercase file endings and add a NC (not-case-sensitive) to the rewrite-rule flags (as I did above).
Be sure to alter the domain-name to match your domain, but I guess you know that :)

Thanks alot for your Help.
Now it works

Cheers and i wish you a very good Day