why my mentor said me that " You should focus on reading other people's codes instead writing your own " why he said that?

Answer 1

Look for other mentor while you could.

Answer 2

Calviղ 😁😁😁
l hope that your mentor want meant that you have to learn on other code but that "instead writing your" seem say another thing 😕
Anyway, if you want LEARN you have to do much much much practice (in every sector works in this way but programming is an sector much practical)

Answer 3

No idea why your mentor would say such a thing without supplying proper context.

Most things have been done before, so repurposing code is important for saving time. You have to become familiar with the tools available so you know which to use when. But it's hard to know how to use and adapt it in your own use case if you don't know how to code (through practice) or when existing tools won't be good enough (so you will want to create your own).