How much should I train? How much is too little? How much is too much? Well, diet and exercise are not that simple. Every single body is unique and has its own demands, but even more, our bodies change and evolve constantly, and their demands change with them. The training volume that you did last month may not be suitable for your anymore today.
Training is putting stressors on your body, thus making it uncomfortable, so that it then adapts to the discomfort by either growing more muscle (in powerlifting), or increasing lung and heart capacity (in endurance sports). These adaptations happen during recovery. Therefore, it is always best to under-train then to over-train. Muscle fibres are ruptured during training, and recovery time is when they grow back, but in an increased strength and quantity. This causes hypertrophy or muscle growth, which then allows progress in training.
A recommended amount of rest days for a recreational athlete is around 3 days per week, but that hugely varies depending on the amount of activity that the individual does outside of training, the lifestyle factors, their diet, as well as the intensity of the sessions.
Recovery happens much faster when the individual is under a low amount of stress, gets sufficient sleep (8-10 hours) and eats a well-balanced diet. Living a balanced life will allow the individual to have less rest days and make faster progress than someone who does not pay as much attention to their lifestyle.
The amount of training that is best for a person depends on a large variety of factors, and it is impossible to provide a universal number of sessions that will work for everybody. It is only by analysis and trying out different fitness routines that you can find the best training volume for you.