practice 2

I recommend him to your company's finance manager position.

He had has worked with our company for 3 years, so I can say I am a person who knows him well.

He was is a diligent and competent person.

Since his major in university was accounting in university, he was is well qualified to have and has adequate knowledge for this field of works.

He was is a person who came to the office earlier than other collegues, and who left at last.

I admit his contribution to our department was very significant.

Entire department employees got  were motivated by his behavior, and this inflowed positive cycle to other departments as well. 

That phrase right there is a little odd.  You also might want to try a different word instead of "inflowed"-- it doesn't fit right in the context of what you're trying to say.

Cooperation with other poeple was an important part in of his job, and he never caused troubles with collegues.

You will not be disappointed once you hire him.

Overall, very good practice!