How to say "I understood" in any other way?
Are there any ways of saying that you understood something except for "I understood"?
I see... / I understand... / You are right... / Right...
Got it / Gotcha / Ah... OK... Understood / You're right about that... / Makes sense...
In my experience, as a non-native speaker of this language, these phrases aren't universally applicable. Every usage situation is somewhat unique.
The choice of the right phrase depends on the context. Plus, when we interact with others, we have little time to make a logical choice. So, there are some rules, but they are easily broken in real-life conversation.
It can be also a matter of a personal habit.
I have an American friend who says "Gotcha" in both formal and informal situations.
And I know people who tend to use formal expressions even in informal situations.
So, my advice would be to go with context, see various examples of how natives are using these phrases, and... basically... try to say what they say in the same situation. And don't be afraid to make mistakes, because even natives do not always follow the rules. :)