When being overtaken, you must do everything you can to make it easier for the overtaking driver. You do this by keeping to the right and maintaining or reducing your speed.
If there is a hard shoulder, it may be advisable* to use it while being overtaken. However, you are not obligated to drive out onto the hard shoulder, as long as it is not required to make way for an emergency vehicle.
If the road is narrow, crooked or has a lot of oncoming traffic and you are driving a large vehicle, or are driving slowly, it is especially important that you reduce your speed and keep well to the right.
Do not fix your eyes on the vehicle that is overtaking you, as this might cause you to start driving diagonally or miss important things on the road ahead of you. Instead, look far ahead of the car.
* Do not use the hard shoulder in darkness or when visibility is reduced or obscured. It is prohibited to use the hard shoulder on motorways and clearways.