i think i can clear a few things up…
dekiru - depending on the intonation can mean u did something hard, or you’re expected to be able to do something unexpected (like win vs a top player), or to remind you that you can win.
ii yo - said when u do something good.
oishii - 5star i’m sure got it from japanese players because it’s very common here for a teammate or a friend to say. it’s just like ii yo, but stronger.
yasu - literally means cheap, but in 3s, it means the combo u did sucked and couldve done much better.
hope i helped.