Give examples of the transformation of mechanical energy into internal and internal into mechanical.

The crane lifts the load. In this case, the mechanical energy of the crane increases the internal energy of the load, in this case the potential energy.
We pump a ball with a pump. The mechanical energy of the pump piston movement is transferred into the internal energy of the compressed air in the ball.
When fired from any firearm, the internal energy of the gunpowder in the cartridge is converted into the kinetic energy of the bullet.
In a car engine, the internal energy of the combustion fuel is converted into mechanical energy from the piston.