how do I get the master Giutar and firefly?

You should check this website out 😉

http://www.carls-sims-3-guide.com/skills/collecting/butterflies.php

you need the Virtoso trait to learn the master tracks, otherwise reaching master guitar (lvl 10) is pretty simple, and all tracks you can learn you can buy in book stores except the 3 master tracks..

I can't remember where the firefly is, but you can easily find it in a guide or ... keep searching 😛