Upgrade to biggorons sword
1. go to kakiriko village and talk to the woman that is standing next to the fence where you put the cuccos when you were a kid. talk to her and she will give you tha pocket egg. once hatched. go wake up talon in the same village and then go back to the woman and show her it. she will give you cojiro
2. go into the lost wods and turn left. there should be a man sitting down. hand him cojiro and he will give you a mushroom.
3. take the odd mushroom to the old woman in the postion shop at kakiriko village. she will give you an odd potion
4. take the odd potion back back to where you found the man. he will not be there. give the potion to the little girl. trade it to ther and you will get the poachers saw.
5. take the saw to the carpenter at geurdo valley. he will be standing outside of the tent. he will give you the broken biggorons sword.
6. take it to the goron on top of death mountain and he will give you the prescription to take to king zora.
7. take the perscription to king zora and he will give you an eyeball frog.
8. take the frog to the professor at lake hylia. he will make some eye drops to take to biggoron. take them to him before they spoil. and don't warp inside death mountain!! they will be expired if you do. he will thne give you the claim check.
9. bring the claim check back to him in 3 days. i suggest using the suns song to make time go by faster.
10. give him the claim check and you will have yourself a brand new sword! it's stronger than the master sword and won't break like the giant's knife.