Help needed with separating of Wp-MultisiteWebsites

Hi, I've tried that for months now, made every thing I could, have read every article on that topic that I've found but had no luck:

We urgently need to get 3 sites out of a multisite installation. The entire volume of GB's in the FTP is about 10-15GB.

the sites are
http://reiseziele.ch
http://denkmalpflege-schweiz.ch and
http://events24.ch

They are all being delievered from the main site http://belmedia-websites.ch

Can you please find us someone who will solve this problem and do it for us?

thanks!!
Albert