You NEED to get to an MSF rider training class before you hurt yourself.
While waiting to do that, find a nice, clean open parking lot to practice your braking.
It sounds like you are riding at a nice, smooth slow pace if you are letting the engine do all the braking. That is fine, and a decent technique to use, when just coasting down from speed at your choosing.
The problem is, when a car turns left out in front of you, your rate of deceleration is NOT going to be smooth, easy or at your discretion.
Start by braking straight and becoming familiar with your front brake. You WILL need to master it's use to stay alive on the street. When the shit hits the fan, it will not be at a time or place or at a speed of your choosing.
Begin slow at like 25 mph. Roll off the gas, clutch in and squeeze on the front brake. You can drag the rear brake at the same time to help, but on pavement 90% of your braking is going to be done by the front tire.
Do circles around the lot. Get up to speed, and then brake. Practice, practice, practice. Every ten laps pick up the pace a little and gradually increase your lever pressure until you are getting good weight transfer (front end dive) and you are used to going from 50 mph down to a complete stop, downshifting, and then doing it over again.
Do not GRAB the lever. Get to it quickly, then squeeze it on. As you roll to a stop in the last few feet, start easing off the pressure, to make a clean smooth stop, while tapping down gears.
It takes time. Repetition is your friend. You are programming your brain. "Muscle Memory" and getting to know the feel for the proper pressure, weight transfer, and traction.
Gradually increase speeds and how quickly you stop. It is an art. One that will save your life.
In time, you will be able to stop on a dime, without ever looking at the levers or even thinking about all the various steps involved.
Find an experienced biker to help show you. Then spend the time to learn how to do it properly.