last night

I worked late last night because I had a lot of outstanding work 
I have been working very hard when my boss complained me that my work isn't good.
Then I told him that I haven't finished my job yet.
I was at middle of my work when he was judged me but
at the end of day I showed him my work and he looked satisfied.

Last Night

I worked late last night because I had a lot of outstanding work to complete.
I have been working very hard when my boss complained me that my work was not satisfactory.
I explained to my boss that I have not completed my work yet.
I was not finished with my work when my boss judged me but at the end of day I showed him my completed work and he was satisfied.

Ashkit's corrections are good, but I think the sentences above are better.

Good job Jose, and keep practicing!