A colleague is a person you work with. A fellow is a rather old fashioned word for a man, and is a word you may find in a fairytale. It is used nowadays to describe medical doctors, or other type of educated scholar (part of a fellowship).

Yes it seems fine.

I'm British so I would say: Life has improved so much recently or Life has improved a lot recently If you are talking about your life, you could put 'My' on the beginning to make it clear.

In five years time, the industry I would most like to work in is manufacturing. This is because the industry manufactures goods such as cars which are in great demand and you can earn a lot of money

http://images.mentalfloss.com/sites/default/files/styles/article_640x430/public/sinister-smiles-primary.png

It's a smile that is a bit scary. Perhaps if someone smiles, but they don't mean it because they are going to do something bad.

A) I'm seeing You say this in the present, because it is clear from '2 o'clock' that it's in the future and it is a definite arrangement. When you are making a decision use will; use going to after a firm decision has been made. Often they can be used interchangeably with no difference in meaning. Even if you mix them up, a native speaker will understand you.

You could say 'There's a tree among the trees.' which is grammatically correct but is confusing. There's a tree amongst some other trees. - this makes more sense, as you are talking about the same thing, trees.