Trying to look can be translated as

Essayer d’avoir l’air.

But for the second part, it depends of the context: “in foreign language”, does that mean you’re doing as if you could talk it, pretending to be fluent, or you want to express the language you’re using?

If it’s the latter, it would be something like:

J’essaye d’avoir cool en parlant Anglais.

Note that “cool” can have many different translations, depending of the “politeness” you want: it could be translated like classy:

J’essaye d’avoir l’air classe en parlant Anglais