Most people start with this mindset but many give up after some time. Most get stuck at 3* or 4* at best, not because of lack of potential but because of lack of interest.
Mentorship is not mandatory to become a successful competitive programming. Actually, if you wish to excel there’s no mentor who can help you achieve that, as nobody will dedicate good portion of their time to you.
Stop looking for some way to improve quickly, sit down and solve some problems. You probably won’t be able to do 6-7 hours at first, it will either be too easy or too hard so you’ll get bored quickly, but once you settle on a decent problem difficulty that suits you well if you stay on your track it will become interesting. Keep in mind that there are many problems that are so-called ‘ad-hoc’ meaning there’s no specific algorithm that can solve them, but rather you need to develop your own. This is why you need to just practice your problem solving ability, rather than study from books or tutorials (of course when you encounter an algorithm needed for a problem, read a tutorial on it, but don’t learn algorithms to solve problems - solve problems to learn algorithms).
Good luck on your journey! Have fun