Hi there. I decided to try my hand at the dialogue files.
I can't call myself a professional, but I try my best.https://www.mediafire.com/folder/a8gv9c6bm6efd/YGO_GB1_Translation
I initially tried to crunch it into the text limits myself, but it is definitely tiresome work. And I realized it meant more to do the text in full and have it done than burn myself out.
(Especially if I'm doing it for someone else and they don't know yet.
(btw, this site is real nice for mocking-up text boxes in this game and a ton of others, if you didn't know that already) https://deathgenerator.com/#ygodds
One more thing is I didn't know what expletive each くそ should be. In terms of translating character dialogue, that word can run the whole gambit from 'darn' to 'fuck' depending on context and personality. I don't know this series quite well enough to do that, and the official English release is infamously G-rated to a fault, so I just marked them all *swear* and I'll have to leave that to you, as well.
And the dueltext file only had a few lines that weren't already handled as well as I could do them.
The card descriptions aren't included, as I only just started those, but I'll try to get through that next. I've been mostly just checking to see if they're just kana-only matches to the Japanese flavor text, and translating them if they're different.
Let me know if I can do anything else, and good luck!