Can you please help me to check my motivation letter?

Hello there. Actually it's my first experience of writing any kind of letters in english. So I hope you will help me to check my motivation letter.
I have some particular questions:
1) "And it is one of the reasons why active sport and active social position became parts of my life."
Is it possible to use past indefinite? Or I have to use present perfect, 'cause "actiive sport and active social position" are still parts of my life.
Is it possible to use word "did" in this sentense? For example:
"And it is one of the reasons why active sport and active social position did become parts of my life." - if I want to try to highlight this sentense, to make verb "become" stronger.

2) " I have started to work with technical units when I got my first chance."
Is it possible to use present perfect tense with past indefinite in the same sentense? Here I try to say, that "I have started...", so I still work with technical units now.

Thanks you for answers!

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MyName MySurname
My_Address
Phone: my_phone

E-mail: my_mail

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Date,
Address

Dear Mr. or Mrs.,
I am in my final year as a specialist degree student in mechatronics and robotechnics systems. I have been interested in technics and technical devices since childhood. That is why I decided to go to technical university, directly linked with industrial field. My profession determines a wide range of knowledge, I must own. I have been trying to achieve maximum success in education, since elementary school. I have always been attracted to all academic disciplines. Each discipline requires a different active approach. Therefore, activity and active search is part of my profession. And it is one of the reasons why active sport and active social position became parts of my life.
I have started to work with technical units when I got my first chance. For about two years I had been working with many various household appliances. I tried to learn everything about devices surround us, and about the ways technology will continue to evolve. After accumulating some practical knowledge and skills I decided to start to work as an engineer in my university’s engineering center. I am very attracted to work with industrial equipment and industrial machines. My goal is improvement in this field.
It is a dream for every professional, especially young engineer, to work in a large international company, one of the world’s leading companies in the industry. And it is a great chance for young professional to obtain this employment and become a professional engineer, as for large company young engineers are energetic self-organized individuals, devoted to their work and company.
Sincerely,
MyName MySurname