What is the purpose and full prompt of your essay? Are you preparing for IELTS or TOEFL?
19 century
Since the 19th century. Why do you choose to write about the 19th century in your introduction?
everything changes
everything has changed
because of these reasons.
This part is not necessary.
didn't
Avoid using contractions in your essay.
take every avenue going
often travel/visit
was not thought so important
was not given much priority
China is raising its population
There has been an immense increase in the population of China
a seriously problem
a serious problem
You should pay attention to your grammar!