Here's a breakdown:
* Mae: This is the verb "to be" in the present tense, third person singular. It roughly translates to "is" or "there is".
* iaith: This means "language".
* arall: This means "other" or "another".
* cyda: This means "with".
* fi: This means "me".
* hefyd: This means "also".
So the phrase translates to "Is another language with me also", which is a polite way to ask someone to speak another language with you.