Without a doubt, one of the basic knowledge to be a good citizen is first aid, since it will depend on whether a person who has suffered an accident or the sudden manifestation of some disease will survive until the arrival of an ambulance.
The more people learn first aid, the greater the probability that you will survive an emergency, wouldn't you want someone with knowledge of first aid to be around when you have an accident? The other option is to have many people around with good intentions, but without the knowledge to perform the necessary maneuvers, which will surely cause your injuries to get worse or even die ...
Immediate attention will ensure that your initial injuries do not get worse, which will help you recover much faster and the consequences are minimal, isn't that great?
The person who needs help can be a family member or friend, wouldn't you like to have the right tools and knowledge to help them? Inevitably one day you will need to apply this knowledge in your inner circle, the health and well-being of those around you will depend on it.
You can look for accessible training courses in your area, the Red Cross and other institutions offer these trainings to the general public, you can also choose to train online, but I recommend that you look for face-to-face training since the practice you will do is irreplaceable.
It may seem like an exaggeration or a cliché, but learning first aid really saves lives, you don't need super powers or a magic wand, you just need to learn a series of maneuvers and apply them at the right time.