The only way to do 3-4 hours workouts daily is to take performance enhancing drugs. Those hired dieticians are controlling diet, workout and drug regime.
Some facts. - I am a professional stuntman, so my livelihood and time are dedicated to this pursuit. Making the time is a requirement. - the time is made up of stretching, skill work, cardio, and strength training. It’s not 3 hours of 1 rep maxes. It is still intense. - lots of people use PEDs and HGH to acquire a temporary physique. However you would be shocked what small changes can do to affect your health, physique, and overall happiness. Adding squats will help you move move better. Yoga will help you feel better, and sprints will shed fat. - consistentcy beats all. Take all the drugs, do all the weekend bootcamps, and try all the crash diets you want. Simply doing anything over a long enough period of time will always yield better results.
What are your characters stats (I don't know how to put it): muscles, bench press, endurance, etc. ?
This place never ceases to surprise me.
E.g. you're not going to manage 3-4 hours of heavy compound lifts a day done in quick succession, sure. At least not without lowering the weights so much it becomes more cardio than resistance training.
Even 1 hour a day is overdoing it for powerlifting type training. At my strongest I was doing 45m every other day. I could probably have done more, but I got my best gains when I eased up and let my body recover properly.
But if you're doing bodybuilding, and a lot of that time are not the big lifts but adding in lots of isolated lifts of various small muscle groups, and sufficiently low intensity cardio takes up a good chunk of the time as well, sure you can easily spend 3-4 hours a day without drugs.
That said, a lot of people clearly claim to be natural while they're not.