That's alright Libor. Le me clarify: -"lhe" can mean "to you" or "to him"; - although you could theoretically say to another person "Do you understand what I tell him?", that's highly unlikely; you probably either ask "Do YOU understand what I tell YOU" or "Does HE understand what I tell HIM".
So no, there's only one way to say "Do you understand what I tell him" and there are actually 2 ways to say "Do you understand what I tell you", but I won't risk confusing you again, and you shouldn't bother anyway, since that second way is only used in Portugal and in certain regions of Brazil (the 2nd person singular).
if you still have questions, fire away! :-)
Well I will be blatant here: How do you say: 'Do you understand what I told her?' Note: I do think it is MUCH more frequent to ask ' Do you understand what I told him?' than' Does he understand what I tell him' for the mere reason that in the latter case you ask for making assumption about someone else, which is silly unless you ask an interpreter which is a real niche of communication.
"Do you understand what I tell her" is still "Você entende o que eu lhe digo?" Yes, you're right, that is more probable. I shouldn't have given "Does HE understand what I tell HIM" as an example. But that isn't a possible translation here. The fact of the matter is that the expected translation is "Do you understand what I tell you" because it is much more probable and therefore makes more sense.
I realize this is a really old comment, but I'll try to answer your questions.
That's not about frequency, we can say whatever we want, right? I think that's because the sentence starts with "você" (you), so that's the context we need to know, in this case. If it were just "eu lhe digo", it could be you/him/her, because there is no context.
"Do you understand what I tell him?" sounds weird to me, Idk if that's correct; in that case, I would say: do you understand what I'm telling him? Same way in portuguese: você entende o que eu estou dizendo a ele? because it's weird/wrong to say "você entende o que eu digo a ele?"
Do you understand what I told him/her? = Você entende o que eu disse a ele/ela?
I just commented bellow that you shouldn't be worry about lhe. I'm Brazilian and I never use it, most people don't. Normally, we would just say: (você) entende o que (eu) digo? or: "(você) entende o que (eu) estou dizendo/falando?".
I hope that helps you and/or someone with the same doubts ^^
The word "lhe" is an indirect object that can mean either "to him", "to her", or "to you". If not clarified, the meaning is taken from the context of the sentence. Since this sentence already references "você", we infer that "lhe" here means "to you". As I understand it, most Brazilians use "lhe" infrequently when speaking and would say "você entende o que eu digo você" to avoid confusion. Would a native Brazilian speaker of Portuguese please confirm?
I am happy I came here since this is one of the most confusing lessons I have seen so far. So to summarize. 'Eu lhe digo' here in this sentence can be translated as 'I tell you, I tell her or I tell him. The 'Voce' in the beginning clarifies that in this context it should be translated as 'I tell you'. Is that correct? Second: can this be replaced instead to 'Eu te dizes' and would it mean the exact same thing?