Then I'll go into detail: let's say he has a real Black Blade (I think that too), no funny theories like painting or strange metals, a real Kokuto; should we assume he forged it himself until further notice just like we do for Mihawk?
If we're going to give Mihawk the benefit of the doubt that he forged Yoru into a black blade, then I don't see why we wouldn't be able to give the same benefit of the doubt to GreenBull. Albeit, GB so far doesn't have a swordsman theme so far, so that could be the only thing one could argue against. Whereas with Mihawk you could argue he fits the Ryuuma-Zoro mold.
But I would say the assumption that a top tier has a black blade and he forged it himself is more accurate than saying he got it from somebody else.
How strong will Hina be eos?
Superior to Prime Tsuru. So between that "YC1" - "Top Tier" range. Of course, assuming Hina peaks out by end of the series, if she doesn't... then hmm maybe YC1 level or so.
Better twerker you or akainu?
If it's twerking for my ladies and putting on a before-bed show then me of course.
If it's for anybody else, I'll have to give it to Saka, magma cheeks just built different man.
Will we ever see Gion actually fight and show us why she was in the running for an admiral promotion?
Final War would be the safest guess, could be against Holy Knights / RA Commanders / Somebody like Yamato/ Marines who'll switch up.
I'd reckon she'd fight some prominent Marine from the new era, in a Marine Civil war scenario. But def. safest bet is Final War for us to know why the Marines consider her a psuedo-admiral.