(Could someone check this daily translation practice :-) Thank you in advance for your attention!)
There has been a growing concern that Japan would deteriorate its national capability. The population growth reached its peak in 2006 and is predicted to decline to one hundred million and 590 thousand (100.59 million) in 2050. Workforce will steadily decrease as the aging society is undergoing simultaneously, therefore GDP will continue to stagnate at lower point. However, being only pessimistic leads us to nowhere. “We won’ to be beaten by rains and winds” as a quote from a novel. It will be ideal to recreate our nation that can offer competition to the stronger, tolerance to the vulnerable while getting together, working together and fostering our children. I assume that our predecessors might have survived their time in that way when suffering poverty.

Your translation is excellent. However, there a few corrections that I would make:

There has been a growing concern that Japan would deteriorate its national capability. The population growth reached its peak in 2006 and is predicted to decline to one hundred million, 590 thousand (100.59 million) in 2050. Its workforce will steadily decrease as the ageing society is growing simultaneously, therefore GDP will continue to stagnate at a low level. However, being only pessimistic leads us nowhere. “We won’t be beaten by rain and winds” as a quote from a novel. It will be ideal to recreate our nation that can offer competition to the stronger, tolerance to the vulnerable, while getting together, working together and fostering our children. I assume that our predecessors would have survived their time in this way when suffering poverty

(aging = a US word, ageing = UK)
Sorry I can't highlight or underline the changes so that you can see them clearly, but what I have written is correct. Please also see some differences in punctuation that I have made.