Help me to correct this please.

This is my resume, please help me.

I have been working for two years since I graduated from the university in June 2012.
I was a trainee in a insurance company for 5 months (2011/7-2011/12). So, My job there was telemarketing. My duties included calling the strangers everyday to sell my insurance. I learned something from that experience. Firstly, I must remain patient when talking to all kinds of people. Secondly, I needed to practice my presentation skills. Thirdly, it let me know how important courage it is!
I stayed at home to help my parents’ food store for a whole year in 2012. I sold food and cleaned everything after customers finished with the food. Actually, I was a waitress. I felt that I made a valuable contribution and was thankful to my parents.
I worked in company involved with communication during 2013. My job was sorting out data. I have become more careful and observant as a result of this work.

[Good work.  Some of my corrections were to make the sentences sound more natural in a resume.]