My new guitar is Yamaha f310.
The original strings were medium but I changed them to extra light .. because I found them easier to play, and have a brighter sound ! But all I hear is a buzzing sound, terrible music . Some people told me I have to have my guitar setup ..but I can't go to a professional guitar expert right now , and every time I ask question I do not find clean short answers :( So , here are my questions : (I'm 100% beginner ) 1 - The Neck Relief : Does it mean that it must be dead straight?

2-The saddle ( adjusting the action) Do I have to lower the saddle or make it higher ?

3- Strings Height : I don't know what the right strings height must be !? how many mm?