Understood or Understand
For example, in a casual conversation with a person from another country, the person said you something and you want to answer that you have got it. Which answer would be more correct:
"I understand"
or
"I understood"?
I used to use the second one, but today after a conversation with someone who also learn English, but is not from my county, I have doubts about that.
In my native language which is Ukrainian if one says "Я зрозумів" which is translated into English as "I understood" it means that the meaning of the previous message is clear, it's understandable. But if we say "Я розумію" which is translated as "I understand" it means that we understand not only meaning, but also the way of thinking. For example:
— Coffee isn't a healthy beverage, but I was very sleepy in the morning, so I've drunk two cups of it.
— I understand! I also drink it a lot.
Please tell me when we should use "I understand" and "I understood".