Hello Zilin,

I might write the passage like this:

Self Evaluation [1]

With my 6 years of [2] experience in Spine, Trauma and Joint, I went from being a freshman to be a true engineer. In the past 6 years, I improved my machining process knowledge, verified the ability of my design and drawing ability and studied the orthopedic surgical surgery. In At the same time, I enhanced my knowledge of medical device regulations. I also improved my management skills for of programs and projects. I want to study continually, want to and be a knowledgeable engineer or even a manager.

[1] I would remove the hyphen. A hyphen (-) is used to form a multiple-word "phrasal adjective". In your case, Self is only a single word adjective describing the noun, Evaluation.

[2] While it is true that is spoken English, we may say “6 years experience”, in formal written English, we should include of as a preposition between years and experience.

I hope that helps you, Zilin!