One Chinese graduate student to RWTH need a large and convenient flat , with rent fee <400 Euros, nach < 600 Euros.

I'm looking for a flat with ideal traffic conditions, which means bus stop around this can take me to Super C in 20 minutes. It would be perfect if there is a park or a train station close to the flat.
The flat must have the kitchen and the bathroom, it's better if equipped with a bike garage . Net work speed is also important, WiFi can't be lower than 20 M/s.
As to the furniture, I need the flat fully-furnished with bed, bookshelf and desk and even the bike, I can pay more than 600 Euros for all the furniture if they are all in good conditions.
My total budget for the rent is 350 Euros, however, if the location is better than my expect I can increase it to 400 Euros and I'm able to pay it on time per month.