My specialisations are in the German and English languages.
My specialisations are the German and English languages.
Is "specialisation" here appliable to both of the sentences? Also, Should I use "language" instead of "languages"?
Both sentences are correct, it just comes down to flow and personal preference at this point.
Personally, I would reword the sentence to something like this:
My language specializations are German and English.
