@Reda Belakhdar I think you definitely can give good advice, even when you didn’t achieve the skill, maybe even better than someone who achieved the skill. There are so many coaches in Gymnastics, Football, Basketball etc. who wasn’t top athletes and still train the best in the sport. In my opinion it comes to specific knowledge. Sure if you watch 5 YouTube tutorials you shouldn’t give advice, but if you have 10 years coaching experience and trained many top athletes than you have the specific knowledge to give advice. Than you know how the skill works, where other athletes had problems and also how they overcame it. That’s the difference, a top athletes only knows how he progressed, a good trainer knows how hundreds of athletes progressed, and with that can give you better advice (for your specific situation) Let me know if you have the same opinion or not :)