Its not "How many kill" in a match. Its about "how you kill" enemies.Lets say you get aces in bronze lobby. There are 2 ways-

1. try to tap and burst your shots to get headshots. (Good practice)
2. Spraying and crouching against 5 enemies and luckily getting killed. (Bad practice)

If you are doing the 1st point (good practice) , you will eventually learn how to control a gun AND also play better against higher ranks and improve your skill and rank.

If you are doing the 2nd point (bad practice) , you will almost NEVER get out of bronze and silver. Because you may luckily get those kills against unaware players by spraying and crouching (which makes you more vulnerable). But you will instantly get headshot and die in higher rank because they have better tapping and burst skills than you crouch spraying.

Also the higher you go up in rank the harder it gets to realize the mistakes you make. People around bronze have very little knowledge about all the agents , spike time, sound and even map angles. So for lower rank people under silver, improvement room is HUUUGE.One of my cousin was silver. He played like an hour a day at most. During his semester break he played 2-3 hours a day and improved ALOT and went from silver 3 to Diamond 1 in 50 days and drastically changed his playstyle.

I suggest if you have a decent PC with high fps, you can use Nvidia geforce experience to save your replay and records to check your own gameplay or use OBS replay buffer if you do not own an Nvidia card. (Since we do not have a replay system yet)

Tldr- Have good practice and get kills with it, Dont do bad practice and praise it.Eventually, you will be the smurf in low rank lobby they are afraid of.