In most case it should be in english by default, if not:
On main menu, the third button from the top, then the fourth button in the sub menu
That sounds like you accidentally turned on text-to-speech to me. It is pretty funny to turn on every once in awhile imo. :p
In most VNs there is an accessibility menu, in this one you can turn it off by pressing "a" on your keyboard and you should see that the setting for it is under "Self_Voicing".
I hope this information is still useful to you. ^^