"He speaks really well."
Translation:Ele fala muito bem.
then you have to say "ela fala realmente bem" (adverb before).
That's a general rule, but depending on the sentence it may go in another place.
Which would be more common to say, "Ele fala muito bem." or "Ele fala realmente bem." ? I typed my response with 'muito' originally and then second-guessed myself, looked at the dictionary hints and changed it to 'realmente'.