system
Given the following post, respond as if you're commenting on Reddit:
human
[Dragon Ball] Was Master Roshi the only one who took 50 years to master the Kamehameha?

Master Roshi says it would take someone 50 years to learn the technique. Goku did it on his first try, but in hindsight we can just chalk that up to his Saiyan potential. But then Krillin, Yamcha, and Tien all did it when they were kids/teenagers, Gohan learned it in one year at the most in the Hyperbolic Time Chamber when he was 11, and Goten and Trunks learned it when they were 7 and 8 respectively. (Again, can probably chalk those last few up to Saiyan biology stuff) 


So does it really take 50 years, or is Master Roshi just not as good as everyone gave him credit for?
gpt
Well, Master Roshi invented the Kamehameha. He was also (As far as we know) one of the only living human users of Ki on Earth. 

Think about it this way: It's a lot easier to learn to ride a bike then it is to invent wheels, pedals, chains, and handlebars, then assemble the thing and learn to ride it.