Need help revising my Enlish writing

[ESLDumbie]

Dear Sir or Madam,

This is my first time here. I have been struggling with my writing in order to convey correct meaning in my following accomplishment summary essay. Could you please help to revise or add needed words to make sense. I am greatly appreciated your help.

In the past year I have made a significant contribution/added value to the team. I take on more assignment tasks/responsibilities than my teammates and preserving successfully complete tasks on time. I was able to balance my work and helping team members. I have also taken over the contractor's work who leaved the company and get the job done within schedule as result saving money for company to hire an new contractor to handle that job. Even the requirements changes, design changes and interface changes, but i was flexible to adapt to complete my assignments effectively and efficiently. I have also provided valuable feeback to the team.

[Mister Micawber]

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In the past year I have made a significant contribution to the team. I took on more assignments / tasks / responsibilities than my teammates and successfully completed those tasks on time. I was able to balance my work and my help to team members. I also took over the work of the contractor who left the company, and I got the job done within schedule, thus saving money for the company to hire a new contractor to handle that job. Even though the requirements, design and interface changed, I was flexible in adapting to complete my assignments effectively and efficiently. I have also provided valuable feedback to the team.
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Native English teacher at Mister Micawber's