Does anyone know how to translate or any method to understand the xfx and / or onomatopoeia of the one piece manga? If anyone knows please give me a hand.
I find The JADED Network to be a good English glossary for Japanese onomatopoeia and mimetic words. Normal Japanese-English dictionaries usually aren't enough to handle the diversity of manga sound effects.
If you don't find a word in there, try fiddling with long vowels or small "っ"s a bit. In this case, I've shortened ガキイン Claang to ガキン Clang, and found it.