Depends on what's wrong with it. Here's a helpful link.http://www.parktool.com/repair/
Yes
the faster the speed of the bicycle,the brighter the lamp
The average bicycle speed is around 15-20 km/h.
Yes, it is possible to fix a bent bicycle rim by adjusting the spokes or using a wheel truing stand to straighten it out.
The standard chain width for a 9-speed bicycle chain is 6.6mm.
It is recommended that you wear a helmet, but it is not a legal requirement
The speed ratio of a bicycle is the (gear ratio* radius of the wheel)/ Length of the pedal arm.
Mark Cavendish's top speed on a bicycle is around 45-50 miles per hour.
The average speed of a bicycle on Google Maps is around 10-15 miles per hour.
An 11-speed cassette is compatible with a 25-tooth cog on a bicycle.
The standard chain width for an 8-speed bicycle chain is 7.1 mm.
Braking reduces speed.