Try that again.
OK I'll walk you through it. the link claims that 68%(or roughly a 2/3) of that countries murders were committed with fire arms. murder is about killing people, it's about wanting them dead, not about having a gun and wishing you had someone to use it on.
the fact of not having guns legally available does nothing to address the real issue of the murderers wanting to see the victims dead, and their willingness to make that happen.
so if this program is 100% effective and even the criminals give up every gun in that country, when someone wants to kill another person (and it seems to happen a lot in Brazil) they will just have to find another means, as the other 3rd of the killers did last year.
or if you want the short version. to quote Archie Bunker (regarding the 86% who were killed with firearms)- "would it make you feel better if they was pushed out of windows instead"