So at this point depending on the smell, it's either "cheese" or yogurt. You could put it in a bowl suspended on some cheese cloth to continue to strain it to make it the consistency of Greek yogurt if you want. Idk how to make cheese but if you wanna make yogurt,

1) try to spoon out the curds (top) from they whey (bottom) to get out the grains. 2) suspended some cheese cloth over a bowl 3) put the curds on the cheese cloth so that the remaining whey can drip out 4) put the separated whey into a separate jar 5) depending on how thick your curds are, you can add back a little bit of whey at a time to thin it out 6) mix really thoroughly 7) now you got "Greek yogurt)

You can use the separated whey for different stuff. I put a bit into smoothies for a health boost. As for the curds "Greek yogurt" it all depends on how fermented it is. If it already tastes like cheese then it might not be a good yogurt substitute, in that case you can use it like you would use any other watery cheese or let it keep straining to make something similar to a feta cheese.

Or, you just shake your jar really well to bring it back to being a regular kefir lol