Yo estoy deacuerdo/I agree:

Much confusion is prominent with these terms (Yo estoy deacuerdo/I agree) in our Skype English classes as the types of words are different. If we say ‘Yo estoy deacuerdo’ we have the subject, verb and adjective. The correct translation of ‘yo estoy deacuerdo’ would be ‘I agree’. Here in the English we have the subject and verb only. It is very common for most students to say ‘I am agree’ as they translate literally, word for word, from Spanish to English. As ‘agree’ is a verb and not an adjective, the same word order can’t work when translating from Spanish to English. In other words, we can never have the subject, the verb ‘to be’ followed by the infinitive of the word ‘agree’. If we consider the sentence ‘she (subject) is (verb ‘to be’) cry (infinitive)’, you can probably make out that this sentence is very wrong. The same goes with ‘I (subject) ‘am’ (verb ‘to be’) ‘agree’ (infinitive)’. It really doesn’t work. So now you can see more fully why ‘yo estoy deacuerdo’ should be translated by saying ‘I agree’.

Similarly, ‘no estoy deacuerdo’ would be ‘I don’t agree’.