Umm I didn’t say 3x3 
I said work up at to heavy triple for a single set, so say 125-130kg x3 for you. You try and increase this over time as you get stronger, it should be going up quite steadily.
Rest 3mins then drop the weight down 85kg and do 4 sets of 2
Each rep is to be lowered in 8 secs (keeping breathing), paused for 2 secs at the bottom (keep tight) and then exploded up. You rest about 2 to 2.5 mins between sets.
You may want to do only three sets since it will be hard and you will have DOMS. Then 4 sets of 2 the next workout. Try and add 1-2kg to this 85kg everytime you do this workout- within reason - or you can just add one extra set rtaher than increase the weight, and then next workout add some small amount of weight and drop the extra set.
Oh yeah make sure you do actually lower in 8secs and don’t cheat yourself by going faster even if it hurts
I myself will follow this up with 2sets of 8-10 single leg work - bulgarian splitsquat or stepups, couple sets of glute ham raises or single leg back extensions and some ab work
When done right you will notice increased muscle size as soon as the next day!