I often make mistakes in writing English.
:D .... Well... we all do :D What is more important is that we learn from our mistakes : )
At the end of the example, I wrote "He thought out of the box and solved the problem completely." I think it kind of demonstrate my originality in thought. Do you think it is too weak?
That line is grammatically fine. I don't get what you mean by "my originality in thought". This is Andy who solved the problem, didn't he?
So, your role there is not clear... Without having any idea as to why you write this, it's difficult to comment on this :(