How to disable accentuated char suggestion on long click on mac? When pushing a key for a long time, you expect to print a lot of times the same char. 
Instead of that, I now have a popup suggesting all accentuated chars. 

How to disable that and come back to a classic keybaord function?
As given in the link by Tom Gewecke, you can disable the Character Picker by typing the following in a terminal : 

defaults write -g ApplePressAndHoldEnabled -bool false