Ok thank you so much. Why is that dangerous? Im curious about. Can I regulate voltage with a potenciometer?
In the simplest terms I would say that it is being implied that if you have to post for guidance on a circuit that uses mains voltage then you probably should not be messing with mains voltage. It is almost impossible to completely train someone to work with mains voltage safely in a few forum posts. You are therefore being advised to buy a factory made power supply.