Hello Marcia!  I've made some corrections below.  This is a great post and easy to understand, well done.

correct me

I've graduated from law school and agribusiness, but I intend to proceed with my law studies and law career. I've never had a problem in my college with grades or discipline.
I don’t have a problem in working in groups, actually, I like it, because we can debate and exchange experiences and ideas.
After my studies, I want to work hard to become a good lawyer and I'll be always to study, because I also want (in the future) to become a judge, for this I need to have experience.
So in this midle time, I want to study at American College to expand my knowledge and vision. I’ve been reseaching and I found this opportunity in this institution.
I’m interested in a Public Law, specifically in Constitutional Law, Administrative Law, Environmental Law and Tax Law. I’ve been interested in human rights and Universal Declaration of Human Rights, so I intend to work at the Organization of the United Nations as a volunteer. It’s interesting, because our Constitution was based on this Declaration.
My thesis in a college was Control of Constitutionality and I had an opportunity to learn a little about American Contol of Constitutionality, because our system was based on the American and Austric Control.
My goals are shared experience about brazilian law and american law, to compare, to have a larger vision of law, besides I want improve my english (law english).
I’m very comitted to my career, to follow my dream and to become a successful person.

correct me

I'm graduated in law college and agribusiness, but i intend to continue with my law studies and law career. I've never had a problem in my college about grades or discipline.
I don’t have problems in working in groups, actually, I like, because we can debate and exchange experiences and ideas.
After my studies, I want to work hard to become a good lawyer and I'll be always studying, because I also want (in future) to become a judge, for this i need to have content?.
So in this midle time, I want to study in an American College to expand my knowledge and vision. I’ve been reseraching and I found this opportunity in this institute.
I'm interested in Public Law, specifically in Constitutional Law, Administrative Law, Environmental Law and Tax Law. I'm interested in  human rights, Universal Declaration of Human Rights, so I intend to work in(or for) an Organization of the United Nations as a volunteer. It’s interesting, because our Constitution was based in this Declaration.
My thesis in college was Control of Constitutionality and I had an opportunity to learn a little about American Contol of Constitutionality, because our system was based in the American and Austric Control.
My goals are to share experience about brazilian law and american law, to compare, to have a bigger vision of law, besides I want to improve my english (law english).
I’m very comitted to my career, to allow my dream and to become a successful person.