I wonder the exact meanings of 'to get something across to somebody' here in these two sentences.

Could you please explain them to me?

1.Your meaning didn't really get across. (=Your meaning was not clear and somebody didn't understand it...?)

2.He is not very good at getting his ideas across.(=He is not good at explaining something or telling what he wants to tell somebody, or sharing information with somebody...?)

I looked it up in the dictionary and it shows three definitions of this verb, but I still decided to ask about it because I am not sure they are clear to me especially this one: 1.'to succeed in communicating something." Does it mean to share some information with somebody successfully?

I decided to type another definition of this verb to ask if all of these definitions can suit these sentences or only one of them?

2.To be communicated or understood.

Hi Ninania

First sentence I would write it as "You did n't really get your meaning across" and your interpretation is correct.

Second sentence you have correctly understood.

And a further yes for your interpretation and verb use.
Thank you.