Could someone, please, correct my mistakes in this short text bellow?
There are much sickness in society, everywhere. It happens not only nowadays, but happened in the past too. Wars, slavery, inequality between men and women, genocides...the list is long. It seems that mankind never learn with its own mistakes. Your starting point is beyond dispute. Society is definitely sick.So, what? Is there something we can do?
It is not so easy, but I think the answer can be yes.
First, we can not change the world, but we can start changing ourselves. We can change the sphere around us. If we change the way we see life, they we act ourselves we can live better and have some progress. Just being pessimist does not help.
I can not refrain myself of quoting Gandhi when he said "Be the change that you want to see in the world."
I am always struggling to write well in English as my second language. Thanks for your help.

Question

Could someone, please, correct my mistakes in this short text bellow?
There are much sickness in society, everywhere. It happens not only nowadays, but happened in the past too. Wars, slavery, inequality between men and women, genocides...the list is long. It seems that mankind never learn with its own mistakes.  Your starting point is beyond dispute. Society is definitely sick.So, what? Is there something we can do? 
It is not so easy, but I think the answer can be yes.
First, we can not change the world, but we can start changing ourselves. We can change the sphere around us. If we change the way we see life, they we act ourselves  we can live better and have some progress. Just being pessimist does not help. 
I can not refrain myself of quoting Gandhi when he said  "Be the change that you want to see in the world."
I am always struggling to write well in English as my second language.  Thanks for your help.

Answer

There IS much sickness in society, everywhere. It happens not only nowadays, but happened in the past too. Wars, slavery, inequality between men and women, genocides...the list is long. It seems that mankind never LEARNS FROM its own mistakes. Your starting point is beyond dispute. Society is definitely sick.So, is there something we can do?
It is not so easy, but I think the answer COULD be yes.
First, we CANNOT  change the world, but we can start changing ourselves. We can change the sphere around us. If we change the way we see life, they we act ourselves (THEN) we can live better and MAKE some progress. Just being PESSIMISTIC  does not help.
I cannot refrain myself FROM quoting Gandhi when he said "Be the change that you want to see in the world."

Your English is excellent. and I like your politics too. I deleted 'so what' because it is a rather dismissive phrase and might be misunderstood. For instance:
"The world is in a bad way"
"So what?" Meaning : "I don't care."
Good luck with your studies.

Answer

There  is a lot of sickness in society everywhere. It happens not only nowadays, but  t happened in the past too. Wars, slavery, inequality between men and women, genocides...the list is long. It seems that mankind never learns from its own mistakes. Your starting point is beyond dispute. Society is definitely sick.So what? Is there something we can do?
It is not so easy, but I think the answer is yes.
First, we can not change the world, but we can start  by changing ourselves. We can change the sphere around us. If we change the way we see life and the way  we act then  we can live better lives and have some progress. Just being  a pessimist does not help.
I can not restrain myself  from quoting Gandhi when he said, "Be the change that you want to see in the world."

Answer

There is much sickness everywhere in society. It happens not only nowadays, but happened in the past, too. Wars, slavery, inequality between men and women, genocides...the list is long. It seems that mankind never learns from its own mistakes. Your starting point is beyond dispute. Society is definitely sick. So, what? Is there something we can do? It is not so easy, but I think the answer can be yes.First, we cannot change the world, but we can start changing ourselves. We can change the sphere around us. If we change the way we see life,  we can live better and have some progress. Just being pessimistic does not help. I cannot restrain myself from quoting Gandhi when he said "Be the change that you want to see in the world."

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A lovely new photo of you João !

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Should be, "...in this short text below?"