I have asked many people if they have ever taken a First Aid/CPR course. Many have not, and some have but it was a long time ago. Haven taken it a long time ago is better than never taken a course. But it is good to take the course every 2 years to stay current on the techniques and content as it does change over time. I have been a First Aid/CPR and AED instructor for both adults, children, and infants, as well as an Oxygen provider for many years now. Over the course of those years, there have been a few changes.
Knowing first aid and CPR at the minimum is the best way to survive in an emergency situation. Knowing how to use an AED is beneficial if you need to help someone at the airport or a place of business, and there are AED machines on the walls. Many times, those systems are not charged and they don’t always work due to improper or lack of maintenance.
Local American Red Cross, American Heart Association, as well as your local PADI Dive shop offer First Aid/CPR classes. I have seen and taken some 100% online courses for review, but I discourage them due to the fact you do not practice what you learn. When I usually teach, I bring an adult, a child and infant size practice dolls for CPR. I also do practical skills for splinting, bandaging, slings, situational scenarios, and more to make sure that they are prepared for anything that they can assist with.
Go take a class, and make sure to do so every 2 years so you are always up to date, and at least practicing every 2 years. Stay away from the 100% online courses, and actually take one in person with a qualified instructor. My favorites have been the American Red Cross and PADI Dive shop training.