The bike was very hard to start and the petrol is pouring through the overflows

You may have a stuck float and/ or float valve. Use the soft end of a screwdriver and lightly tap on the reservoir at the bottom of the carb and try to start again. You may wind up needing to disassemble the carb to free up that float. If you haven't run the bike for a while you may need to get a rebuild kit and rebuild the carb. If you're not going to ride for longer than 2 weeks add some fuel stabilizer to the gas to prevent varnishing of your fuel - it also helps to keep the internals of the motor and carb lubed. Add stabilizer to the fuel and run motor for at least 2 minutes - you actually may want to try this before you take the carb apart or buy the rebuild kit.
Good luck!

Float inside the bottom of carb is attached to a needle that shuts off fuel when the proper fuel height is reached inside the bowl. This tiny needle usually has a rubber tip that is pushed upwards by the pressure of the float. Trash on the seat of the valve, or improper float height are common culprits with fuel pouring out of overflows. you can clear trash of the valve seat by blowing into the fuel port on the side of the carb. You can adjust float height by bending the metal tab that pushes on the needle valve.