There are several causes for the decline in the quality of life for people living in big cities. 

the high population density人口密度高

results in overcrowding导致过度拥挤

leads to increased traffic congestion, air pollution, and noise pollution导致交通堵塞、空气污染和噪音污染加剧

Firstly, the high population density results in overcrowding, which leads to increased traffic congestion, air pollution, and noise pollution. 

causes severe health issues导致严重的健康问题

respiratory problems呼吸问题

cardiovascular diseases心血管疾病

mental stress心理压力

This, in turn, causes severe health issues such as respiratory problems, cardiovascular diseases, and mental stress.

the cost of living in big cities大城市的生活成本

is higher than in smaller towns or suburbs比小城镇或郊区高

Secondly, the cost of living in big cities is higher than in smaller towns or suburbs. 

pay more for housing, utilities, transportation, and food在住房、公用事业、交通和食物上花更多的钱

This means that people have to pay more for housing, utilities, transportation, and food. 

the competition for well-paying jobs对高薪工作的竞争

is also higher in metropolitan areas在大都市地区也更高

In addition, the competition for well-paying jobs is also higher in metropolitan areas. 

work longer hours工作时间更长

have less time for leisure activities or socializing with friends and family休闲活动或与朋友和家人社交的时间越来越少

As a result, people have to work longer hours and have less time for leisure activities or socializing with friends and family.

the lack of green space and recreational areas 缺乏绿色空间和休闲区

affects the quality of life影响生活质量

Thirdly, the lack of green space and recreational areas in big cities also affects the quality of life. 

with the growth of concrete jungles随着混凝土丛林的生长

parks and open spaces公园及休憩用地

have become rare已变得罕见

With the growth of concrete jungles, parks and open spaces have become rare. 

deprives people of the opportunity to enjoy nature, exercise, and relieve stress剥夺了人们享受自然、锻炼身体和缓解压力的机会

This deprives people of the opportunity to enjoy nature, exercise, and relieve stress.

overcome these challenges克服这些挑战

should invest in public transportation应该投资公共交通

increase the availability of affordable housing增加经济适用房的供应

promote green initiatives推广环保措施

such as the creation of parks and gardens比如修建公园和花园

To overcome these challenges, governments should invest in public transportation, increase the availability of affordable housing, and promote green initiatives such as the creation of parks and gardens. 

provide flexible working hours提供灵活的工作时间

allow employees more time to relax and socialize让员工有更多的时间放松和社交

Additionally, employers should provide flexible working hours to allow employees more time to relax and socialize. 

improve the quality of life for people in big cities 提高大城市居民的生活质量

ensure their well-being提高大城市居民的生活质量

These measures can improve the quality of life for people in big cities and ensure their well-being.