(2) I am computer illiterate, so I do not know how to draw lines through your mistakes.
So I will just discuss the mistakes sentence by sentence.
(3) In the first sentence, the word is "depression." Furthermore, the "he or she" and the "his or her" are very annoying and distracting to readers. Of course, I understand the problem. Nowadays we are all afraid to use "he" or "him" to refer to both males and females. You can do two things: (a) Use "bad" English and use "their": who helps others is that the person will forget their own stress and depression. (b) You could change everything to the plural: people who help others is that they will forget their own stress and depression. I forgot: If you use only the male pronoun, some people will be offended; however, it seems that if you use only the female pronoun, people are
more tolerant: for someone who helps others is that she will forget her own stress and depression.
(4) I feel that your second sentence needs reconsideration. It seems to me to be repeating the first sentence. In the first sentence, you write "forget her own stress and depression." But in the second sentence, you again say "forget her own problems." But I think that "stress and depression" are almost like "her own problems." Do you understand what I am trying to say? And the words "it is believed as a new science" do not make any sense to me. I am NOT a great reader, but I feel that other ordinary readers would not understand, either.
(5) The third sentence is very good. I think that you meant "less stress." I would forget the "well-being," I think that "better health, less stress, and longer lives" are examples of well-being. What do you think?
(6) Fourth sentence. You accidentally forgot: is especially ....
(7) Fifth sentence. Great!
(8) Sixth sentence. Very nice. I would not repeat the word "volunteer." How about something like: However, Haupt states that only effective programs can benefit volunteers.
(9) Your last sentence. I think that some writing teachers go bananas (crazy) when students end their articles (especially a short paragraph) with the words "in conclusion." Some teachers say, "Your readers are not stupid. If it is your last sentence, then just say it. Your readers will know that it was your conclusion." So just write "People will receive more ...."
(10) In conclusion, I think .... (Just joking!)