1.• I fully agree with you…• I (totally) agree with ....I am (entirely) of this opinion. • You are absolutely right
2.• You’re quite right when you say…/ • I agree with you to a certain extent.
3.• I share your opinion that…• Yes I agree • I share this point of view / I hold the same opinion
4.• I am on the same opinion as… • I approve on his ideas.
5.• That's right • Absolutely • Exactly • Me too • I see exactly what you mean • That's a good point
Note: The expressions written on the same line have exactly the same meaning and can be used in the same way.