oOverpopulation

You could add more words to describe the subject of what will follow.
For example, ''Is overpopulation a problem?''

I don't think overpopulation is not a problem.

Your sentence is not grammatically incorrect, but an English speaker would more likely write it like this.

The United Nations has written, “The population of sub-Saharan Africa is projected to double by 2050 (99% increase).

Let’s nNotice that the mogreatest increasing ofes in population in poorare projected to occur in countries with low quality of life, low level of education.

The UN text describes increases in population in the future, so we should specify that this.

Increasing ofThe population increase in developed countries is projected to be very low.

Again, using the present '''is'' form of the verb ''to be'' makes it seem like these population increases have already happened. Saying ''is projected to be'' specifies we are talking about a future event.

DThe developingment of African and Asian countries will allow to decrease the rate of population growth.

Be careful using the continuous forms of verbs such as ''developing''.

We still have a large amount of earth with a low density of population.

''Large amount of earth'' sounds a bit strange, as if you are talking about soil. It may be better expressed as ''a lot of space on Earth''.

PThe problem is the overpopulation of certain of piece of earthplaces, big cities solike New York, Paris, Moscow, Hong Kong, and some cities in Japan.

Remember to use articles such as 'the' and 'some' before nouns. The word 'pieces' is better expressed by 'places'.

Many of them go to work in these cities because they can't do itwork in their hometown.

'Do it' sounds a bit informal in written English. 'Go to' isn't incorrect but also sounds a bit too much like spoken English.

We need to develop all countries and aim to not to have cities, where business, money and power are concentrated.

I don't think overpopulation is not a problem.

The United Nations has writwroten, “The population of sub-Saharan Africa is projected to double by 2050 (99% increase).

Let’s notice that the most increasing of populationNote that population is increasing the fastest in poor countries with a low quality of life, and low levels of education.

IncreasingThe rate of population growth in developed countries is very low.

DThe developingment of African and Asian countries will allow tofor a decrease in the rate of population growth.

Problem is overpopulation of certain of pieces of earth, big cities solike New York, Paris, Moscow, Hong Kong, cities in Japan.

I think overpopulation is not a problem.

Instead say "I don't think overpopulation is a problem, it is a consequence...."

United Nations has written, “The population of sub-Saharan Africa is projected to double by 2050 (99% increase).

The United Nations....

Let’s notice that the most increasing of population in poor countries with low quality of life, low level of education.

Instead of "let's notice", say "Noticeably the most increasing populations are in poor countries with low quality of life and a low level of education."

Increasing of population in developed countries is very low.

Instead try," Population increase in...."

Developing of African and Asian countries will allow to decrease rate of population growth.

Instead try, "The development of African and Asian countries could decrease the rate of population growth."

We still have a large amount earth with a low density of population.

"amount of earth with..."

Problem is overpopulation of certain of piece of earth, big cities so New York, Paris, Moscow, Hong Kong, cities in Japan.

Try, "The problem is overpopulation of certain places on earth including big cities such as New York, Paris, Moscow, Hong Kong, and some cities in Japan."

We still have a large amount of the earth with a low density of population.

'Of earth' would also make sense.

The United Nations has written, “The population of sub-Saharan Africa is projected to double by 2050 (99% increase).

Could be, 'The United Nations have written', depending if The United Nations are plural or singular.

Increasing of population in developed countries is very low.

Population increase in developed countries is very low.

PThe problem is overpopulation of certain of piece of earth,parts of the world: in big cities souch as New York, Paris, Moscow, Hong Kong, and many cities in Japan.

Many of them go to work in these cities because they can't do itfind jobs in their hometowns.