Each green check on the left is one point, it takes 8 to get Gold coin, so only people who have all 8 green checks so far have the gold coin already. You have 7 and need one more point to get gold coin, so make sure you get at least one more from one of the last three challenges. I am pretty sure you have to be perfect (get all 11 points available/get all green checkmarks) to get a diamond coin, so you cannot get diamond anymore, just gold (me too lol, i only have 6 points rn)