I want to make a BLDC Hub motor for my bicycle but I am 10th grade and doesn't now so much about electrical engineering
When BLDC motors off, do they affect my normal riding...


Yes. The attraction between the magnets and the steel core fo the windings will cause "reluctance torque" that will be like a small amount of braking. If the coils are connected together through the ESC, there can be generator action that could be used to charge the batteries, but that would add to the pedaling torque unless the ESC is arranged to do that only while coasting downhill.


  how to install hall effect sensors...


What you have drawn is the right general idea. However two pulses per revolution will probably not be satisfactory.

About the ESC

An ESC that rotates is not a good idea. It will be difficult to provide reliable operator interface, difficult to mechanically balance the wheel, and difficult to design a mounting arrangement.

How to design the motor

Motor design is a complex task. Every aspect must be calculated. The torque is proportional to the magnetic flux. Flux is proportional to the area of the air gap, the space between the rotor and the stator. The length of the air gap is also important, The length is the small distance through the air between the rotor and stator. Then you have the strength of the magnets, the number of poles, the number of turns of wire, the voltage, the current, the ESC design etc. The thickness of the wire is determined by the current, the insulation temperature rating and the ability to cool the coils.

Overall assessment

As commented by @Russell McMahon, what you have described is very difficult to do. It would be much easier to purchase the major components and use them to convert a bicycle. A conversion can be a challenging project. You should do that and other less challenging projects before attempting a project of the scale that you have described.