Questions & Answers about Я всё понял верно.
- Я = I
- всё = everything
- понял = understood
- верно = correctly / right
So the sentence is literally I understood everything correctly.
Понял is the past tense of the perfective verb понять.
That means it refers to a completed result: I understood / I got it.
Compare:
- понимаю = I understand / I am understanding now, in general
- понимал = I was understanding / I used to understand / I understood in an ongoing or descriptive sense
- понял = I understood / I got it as a completed event
In this sentence, the speaker is talking about reaching understanding, so понял is the natural choice.