If anyone needed some help, first as you go towards Guardian Ape in phase 1 and wait for him to turn around then use firecrackers. (Any firecrackers would work I think) After that if you use it one more time you notice after hitting him he will be able to crush you and deal damage and to avoid that go to his right side and just attack. The ape will always fall down you after using firecrackers on him after the 2nd time so be weary of that, wait for his combo's to end to use firecracker's, note that he has 2 attacks that can not be blocked, first is the grab you can dodge easily by jumping and the second grab is the the one where the ape jumps toward you but that can be countered by going around him and you get 2 extra hits or maybe even 3! In phase 2 he will probably use a scream attack at the start always to avoid it just run as far as you can out of it, or you can use the umbrella prosthetic, you may have notice that he wields a sword but don't be scared of it. You can deflect him easily now just keep deflecting until he does that overhead slam and just deflect it since it is slow and the ape will go down and you will have the opportunity to use the loaded spear any version will work I think, just press R2 two times if you have the normal one if you have the thrust type you can hold R2 then press it again to release as you do that, you will notice his posture filled up a lot and then see a centipede coming out of it's head. Now he still has 2 attacks that can not be block the first one is the sweep but it can be easily dodged by jumping the second one is where the ape jumps and he will do a sweep attack if I'm not mistaken, you are able to jump to dodge it too. Sorry for the bad English but I hope this has helped anyone.