Your sentence looks good....Regarding your using at before telling the amount, I think a simple comma (,) or hyphen (-) will work better. Then the sentence will look somewhat like - "In 2005, company A produced the highest amount of waste, approximately 12 tonnes, while the figures for company B and company C stood at two-thirds and one third of the amount produced by company A respectively." N.B. I am a graduate in English Literature - not an IELTS expert.

Some sentences came to my mind, please correct them

All is good except a few people.
There may be some reason that makes him become bad.
Situations deviate many people.
For example - a hungry man may steal food to satisfy his hunger.
We can't estimate everyone based on their appearance.

I wrote these sentences to brush up my English.
I think that thinking as well as expressing our feelings in English is the easiest method to become fluent in a language.