Correction in red.  Stylistic changes in blue.

Why I am a Social Worker    (In a title, the "important" words should be capitalized.)

I am a social worker because it is a good job for me where I can help people in need.
I am feeling useful being a social worker.
I enjoy helping people in difficulties and listening to their problems, and I like to try to find some solutions to resolve their problems.   (solutions + resolve is redundant)
However, it's hard for me to be a social worker because we see poverty, problems, and difficulties daily, and it is sometimes difficult psychologically.
I like to help parents to improve their relationship with their children, and make them a smile.
For me, social work is a humanistic job.
I help different members of the public, such as people with disabilities, the elderly, orphans, women without a partner, and working people.

Your post was in a serious tone, so I changed the informal "kids" to the more formal "children".  

You could say, "... such as the disabled, senior citizens, ..."  You can also call the elderly, "senior citizens."

Why I am a Social Worker

I am a social worker because it is a good job for me where I can help people in need.
I am feeling useful being a social worker.
I enjoy helping people in difficulties and listening to their problems and I like to try to find  solutions to  their problems.
However, it's hard for me to be a social worker, because we see poverty, problems, and difficulties daily and it is sometimes difficult psychologycally.
I like to help parents to improve their relastionship with their children and make them a smile.
For me, Social worker is a humanistic job.
I help different members of the public, such as people with disabilities, the elderly, orphans, women without a partner, working people...