Some suggestions/corrections for the English translation:
Original: No directory selected, start without any files!
Suggestion: No directory selected, starting without any files!
Original: Please wait, search for movie files!
Suggestion: Please wait, searching for movie files!
Original: Release 2010-2013
Suggestion: Copyright 2010-2013
Original: ...maybe the list is to long...
Suggestion: ...maybe the list is too long...
Original: Convert listet, and selected file to mp3, wav, ogg, mpeg4 or wma.
Suggestion: Convert selected file to mp3, wav, ogg, mpeg4 or wma. (I'm not sure what you mean with "listet")
Original: Are you sure to delete $SELECT?
Suggestion: Are you sure you want to delete $SELECT?
Original: Play your playlist without display video!
Suggestion: Play your playlist without video display
In the "Settings" window, there is an entry which refers to the Default Directory but it is named "Default Settings".
It should be "Default Directory"
Original: Note: Your current playlist will overwrite!!
Suggestion: Note: Your current playlist will be overwritten
If you like, you can send me the .po file for the English translation and I will make the corrections

Now, one question and one more suggestion...
Question: what is the purpose of "playlists mode"? How does this work?
Suggestion: when you hover the mouse over the different playlist options (loop, shuffle etc), the tooltip always shows the same thing:
"If no files are displayed below the list, you have no playlist generated!"I think that every option should have a different tooltip, explaining its function.
Same thing happens in the profiles window. It always shows:
"If no files are displayed below the list, maybe the list is to long, or no files are available!"