Motivation letter

Dear Sir:
(1) I am writing in response to the internship opportunity available on your website.
(2) I’m writing us and I’m sending my curriculum vitae because of I'm feeling interested in activity the activities of your company.
After so much effort and study, I have finished a few months ago I finished my degree in Mechanical Engineering by from Valladolid University. In my last academic year, with only one subject to finish and with the Final Project finished, I decided go to Australia to improve my English. (A) I have a great interest in the energy field. You can see in my curriculum vitae that I have experience of 6 months experience in the energy renewable energy field, specifically in photovoltaic plants. My Final Project (Study of the potential of renewable energy in the Valladolid University) also is relationated related with this field.
(B) You can see on my Curriculum Vitae that I have worked like as an engineer during 6 months in OBRATEL construciones y servicios S.L.
I am a person with great ability of adaptation, very hardworking and responsible. I learn quickly. I’m sure that you dont won't regret of join me to me joining your team.
Please feel welcomed to contact me via telephone or e-mail if I can give some additional information.
 Thank you very much for your consideration and time,
Kind regards,

Very good Sara. My corrections are in red and my suggestions to sound more natural are in blue/grey. Mostly they were changes to the order of words.

"in the Valladolid University" - Normally you would say either "in the Valladolid University" or "in the University of Valladolid".

"I am a person with great ability of adaptation, very hardworking and responsible" - A more natural-sounding way to say this would be "I am a very hardworking and responsible person with the ability to adapt to different situations"