FTL Silver is the same as Star Alliance Silver. *A Silver has no lounge access benefits (if travelling in economy class), I'm sorry. I know that LH allow lounge access, but only for LH lounges. Other *A airlines do not allow, nor does LH allow *S into their lounges IIRC.
You need to be HON Circle or Senator (ie Star Gold) for lounge access for *A members.
see here:
http://en.wikipedia.org/wiki/Miles_&_More
and here:
http://webwork.staralliance.com/main_ffp.html