Best way to change oil is to heat the motor to operating temperature, remove the drain plug and leave standing for 30 mins for all the oil to drain.
Replace the drain plug and fill with 650ml, no more, no less of oil of your choice.
Good choices of oil are: 10w 30 motor oil, no friction modifiers.
Automatic transmission fluid type F.
Motorcycle gear oil designed for wet clutches, there are a few very good brands, the choice is up to you.