Ambassadors and Translators
Jelly, 19 17 bytes

ŒPŒ!€Ẏj@€fƝẠ$ƇḢḊṖ


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A dyadic link taking the list of translators as the left argument and list of ambassadors (each double-wrapped in a list) as the right argument. Returns a list of translators, each of which is a list of the languages they speak. 

Thanks to @KevinCruijssen for saving 2 bytes!

Explanation

ŒPŒ!€Ẏj@€fƝẠ$ƇḢḊṖ | A dyadic link taking a list of translators as left argument and a list of ambassadors (double-wrapped in lists) as right argument

ŒP                | Power set of translators
  Œ!€             | Permutations of each
     Ẏ            | Tighten, i.e. create a single list of all permutations of any length
      j@€         | Join the ambassadors with each set of translators
            $Ƈ    | Filter those where:
           Ạ      |   all
         fƝ       |   the neighbouring pairs have at least one in common
              Ḣ   | Take the first
               Ḋ  | Drop the first ambassador from the start
                Ṗ | Drop the second ambassador from the end