Seek English translation! "What I said is true!" How to say this sentence in English?

Is what I said true? I'm telling the truth.

I'm serious (I'm not kidding you)

I'm serious, I'm serious (like I'm serious) (not just talking)

I think that's what you need now.

This is what you need.

This is what you lack. Lack, lack

I think it can be added or not, depending on the situation. If you must intentionally emphasize that this is my idea, you can add it. If you focus on the other person's "you", you can leave it alone.