In unplanned, informal speech or writing (e.g. a chat forum) you might say "She speaks English fluently, but she doesn't understand some words though." - but you don't actually need both the "though" and the "but"; you're repeating yourself. It's a bit sloppy. But not as "wrong" as in German, though :-)
Without repeating yourself you might say:
1 She speaks English fluently, but she doesn't understand some words.
2 She speaks English fluently, though she doesn't understand some words.
3 She speaks English fluently. She doesn't understand some words, though.
In the third example, "though" is an adverb:
spoken used after adding a fact, opinion, or question which seems surprising after what you have just said, or which makes what you have just said seem less true:
Two heart attacks in a year. It hasn't stopped him smoking, though.
It sounds like a lot of fun. Isn't it rather risky though? http://www.ldoceonline.com/dictionary/though_2