"agree" is a verb, you don't need one more so "I agree/disagree"

You might hear "I'm agree" from learners because of a translation error. In most romance languages, the phrase is literally expressed as "I am..." In English, "agree" is a verb. "I agree with you" is correct, and "I'm agree" is simply wrong.

I agree with you.

"I agree with you" If you are in an argument with someone who will not back down, and you just want them to stop, you could say "Don't you see that we don't need to argue about this. I''m agreeing with you."