Can someone correct this sentences ? thanks

Great, thank you :)

First, I had decided to pursue an MBA when I was at the university, but I knew at that time, I had to get a master's degree initially and work for at least five years prior to seeking an MBA.

I  hope this helps. =0.)

Thank you very much guys !

-> before doing it

  First of all,    I (have chosen) have decided to (do) pursue (an-an is wrong here--no need) MBA when I was at the university but I knew (at this) that time that I had to get a master's degree and work for at least 5 years  before to do it   

Bonne Journee

Prashant

[the sentences in pink are little bit modified..I hope it looks more appropriate]