Hi,
A convenient public transportation system will - you've moved from 'would' to 'will'. I'd keep it as 'would' here because it is imaginary.
That problem is resulted- This problem stems from..
provide people with good means of travel- provide people with a good way of getting around
posing a huge amount of traffic on the streets- putting...
Things would be better if those people are provided- were provided
under-ground- underground
which enable them- which enabled them
without bring- bringing
motorbikes cars - motorbikes and/or cars
living standards have not been so high- living standards are so high
with cheap and convienient means of transportation- with cheap and convienient transportation
is the pubic transportation system- is the public transportation system
the system will give the- would
