Writing Feedback / [TOEFL] All students should be required to study art and music in secondary school. [13]

I don't know how much time you have but maybe you could express both points of view and then state your own point of view?

Also, you generalise a bit too much. Instead of saying 'everyone' 'all over the world' 'people' and 'nobody' maybe you should say 'many people' 'a number of people' etc.

Writing Feedback / Should Euthanasia be legalized? [16]

A fragment means that it's not a full sentence. It doesn't have a verb. I would try and join it in with the following sentence somehow.

Writing Feedback / How people can gain job satisfaction?/ Factors contributing to job satisfaction [5]

Paragraph 1:
Your second sentence should be joined to the first one because it starts with and so it's carrying on from the first one.
The third sentence is a question so should have a question mark.
I don't think you need the 'among a number of factors' bit
Paragraph 2:
Is there a difference between ones abilities and talents?
'Last but not least' - bit colloquial instead - 'lastly'
Paragraph 3:
The way you've worded it seems a bit strange.
Maybe you need to think of some more reasons why job satisifaction isn't realistically expected of all workers- and maybe some reasons why it is to argue both sides of the point?

Conclusion:
Maybe you could sum up the factors contributing to job satisfaction so you are directky answering the question?

Grammar, Usage / Active voice or Passive voice? Need clarification [4]

I have been doing some research I think I kind of get the idea:
instead of 'Major scenes are accompanied by longer structural units.' it would be 'Long structural untils accompany major scenes.' and instead of ''Lighter pieces are used to entertain the audience.'

it would be 'The audience is entertained by lighter pieces' or 'Lighter pieces entertain the audience.'
Is this right?
Is it a better way to structure my sentences?