Sound issue

Same here. Usually the servant just said the first half and the second half is silenced. For example my Nero(Bride) just chant her poem but didn't said her np name.

I don't know if this is the problem but make sure you have your np set to slow speed. If you have it set to high speed it cuts off part of it.

That may be because of the system specs of your device. I ran FGO on a potato once, it wouldn't even trigger attack animations.
While I would advise against upgrading to a higher end device until you're sure that's the cause, if it bothers you that much, go ahead.