i have few question to ask.. the 1st question is
1) it is possible when we use present tense combine with past tense?
2) Understand and understood.
if i use " i understand what he say" mean now i understand? is it a present tense sentence? if so, it refer to repeated action or true in general?
"i understood what he said". It refer to past.. But now i still understand or not?
The simple present expresses a statement of fact:
Teacher: Max, do you understand?
Max: Yes. I understand.
The simple past expresses an event that happened before now:
Teacher: Max, did you understand the explanation I gave two minutes ago?
Max: Yes. I understood it then, and I still understand it now.
Hope that helps.