In English conversations, people often say that they agree or disagree with each other. There are many ways of agreeing or disagreeing and the one you use depends on how strongly you agree or disagree. Here's a list of some common expressions.
Agreeing in English
"I think you're right."
"I agree with you."
Strong agreement
"I couldn't agree with you more."
"You're absolutely right."
"I agree entirely."
"I totally agree."
Partly agreeing
"I agree with you up to a point, but…"
"That's quite true, but…"
"I agree with you in principle, but…"
Disagreeing
"I'm not sure I agree with you."
"(I'm afraid) I don't agree."
"(I'm afraid) I disagree."
"(I'm afraid) I can't agree with you."
"(I'm afraid) I don't share your opinion."
Note
When you disagree with someone in English, you can often sound more polite by using a phrase such as "I'm afraid…"
Disagreeing strongly
"I don't agree at all."
"I totally disagree."
"I couldn't agree with you less."