A short part of my writing. aw gramma Grammar ramians remains my biggest obstacle -_-

It is sometimes claimed that zoos should be closed because animals are suffering inhuman [1] treatment in some commercial zoos aimed to at entertaining people. For example, animals live in the hostile conditions. To maximize the profits [2], some zoos may cut the staff. As a result, there are no is not [3] sufficient people to keep living environments clean. Even worse, because of visitors’ adverse behaviors, animals may develop some diseases and it is difficult to receive adequate medical cure treatment, accordingly leading to the accidental death of some animals.

In addition, they may overload animals in a narrow area for saving to save space. It This is harmful for male animals which have strong territoriality territorial instincts. Animals may be become sick because of insanitary conditions and fighting. Some zoos do not have specialized medical employees for all kinds of animals and it probably causes the death of some animals. Besides those drawbacks, some zoos buy overseas animals, which are unsuitable to live in other countries, for attracting visitors [4, 5]. Some researches shows that forcing animals to change their way of living may result in a decline in the their birth rate.

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[1] The word 'inhuman' is okay.  However, the word 'inhumane' would be better, and is probably closer to your meaning.

[2] Writing "to maximize the profits" is okay.  However, native speakers will say "to maximise profits".

[3] Why have I changed 'are' to 'is', when you are talking about many people?  The reason is that "sufficient people" is short for "a sufficient number of people", which means a single collection of people.  The following sentences have the same meaning:

"There is not a sufficient number of people to keep living environments clean."

"There is not sufficient people to keep living environments clean."

[4] The corrections provided by Magnus are very good and are more natural.  However, your sentence was not wrong, so I have not changed your words.

[5] This sentence is very disjointed.  Here is a simpler version:

"Some zoos attract visitors by importing exotic animals which are unable to live in other countries."

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Your writing is very good.  I do not agree that grammar is an obstacle for you.  Your grammar is very good.  Great job!

a short part of my writing , aw >grammar remains< my biggest obstacle ;)

It is sometimes claimed that zoos should be closed because animals are suffering inhuman treatment in some commercial zoos aimed >at< entertaining people. For example, animals live in >hostile conditions<. To maximize >< profits, some zoos may cut the staff. As a result, there are >insufficient< people to keep living >environments< clean. Even worse, because of visitors’ adverse behaviors, animals >sometimes contract< diseases>.< It is difficult to receive adequate medical >care,< leading to >the< accidental death of some animals.

In addition, they may overload animals in a narrow area >to save< space. >This< is harmful for male animals>,< which have strong territoriality. Animals may >become< sick because of insanitary condition>s< and fighting. Some zoos do not have specialized medical employees for all kinds of animals>, which< probably >causes the deaths of some< animals. Besides those drawbacks, some zoos >import exotic< animals, which are >unable< to live in other countries, >to attract< visitors. Some [research shows OR researches show] that forcing animals to change their way of living may result in a decline in >their< birth rate.

I give you a B+   Considering that I can't even construct a simple sentence in the language that I'm learning.  Your grammar is very good.   It may not be technically correct sometimes, but I can easily understand what you're saying.