I think it is more like salelling something, you need to saleell something the students needed.

"saling" should be "selling something." "Saling" isn't a word.

Some performe badly in class.

They woaren't afraid of being punished.

You're describing something that's currently true, so use a present tense linking verb to connect the subject (they) with the adjective (afraid)

What is worse is that you can't let them go, because there is school who is watching you.

I think teaching in elementary school is too compleicated, because you have to handle the relationship with students, parents and the school.

I think I am weak inat handling relationship with humans.

And for more, I am so impatient towith the students and I think I am so good that everyone should like me and then performe well.

I am down today.

I'm feeling down today.

I think it is more like saling, you need to sale something the students needed.

I think it is more like selling, you need to sell something that the students need.

Some performe badly in class.

Some perform badly in class.

Some often don't do their homework.

Some seldom do their homework.

They won't afraid of being punished.

They are not afraid of being punished.

What is worse that you can let them go, because there is school who is watching you.

What is worse is that you can't let them go, because there's the school, who's watching you.

I think teaching in elementary school is too complecated, because you have to handle the relationship with students, parents and school.

I think that teaching in elementary school is too complicated, because you have to handle the relationships with students, parents, and the school.

I think I am weak in handling relationship with human.

I think I'm not so good at handling human relationships.

And for more, I am so impatient to the students and I think I am so good that everyone should like me and then performe well.

Furthermore, I am so impatient with the students. I think if I'm good, everyone should like me and they will perform well.

I am so overweening that I always feel sad.

I have such a high expectation of myself, that I always feel sad.

So what I need to do is lowering my expectation and then study another skill to earn more money.

Perhaps what I need to do is to lower my expectation, and learn another skill to earn more money.