Well, this may work for him as he is saving 500 euros every month from his salary and converting to bitcoin. This is a good amount and for sure he can have an early retirement but most of us cannot put that much money into investment in Bitcoin on a monthly basis. The secret here is that if you have more money for bitcoin investment, you will get more profit and hence you can plan this early retirement. Otherwise, with less investment, it will still be good but the money won't be enough to feed you for many years.
Investment is supposed to be long term, there's no such early retirement because you're not looking to make a lot money in short time. It's naive to think the money won't be enough to feed yourself in the future, do you think hold fiat will make you enough in the future? no, the values decline overtime.
Remember we're discuss about money management, not how to earn a lot money. To earn, it's related to get a job that pays well.