What is it called in English grammar when you drop a part of sentence or phrase because it can be easily guessed from the "meaning" or "previous sentences"?

for example :
congratulations (to you)
or (I) didn’t know (that)
or (you) go

In my language there are two types of such removal. one is above and the other is when for example the item (e.g. subject) is already mentioned in sentence:
e.g. I went to there and (I) asked him not to interfere with my job.

just to give you a hint, in my language , Farsi, the word-by-word translation of these grammatical actions are:
1- Removal due to literal-symmetry (or textual-symmetry)
2- Removal due to non-literal-symmetry (or non-textual-symmetry)

P.S. I know these two above phrases don’t make sense in English… but I thought they may ring a bell!
PPS. I don't mean ellipsis