I am a beginner also and have never knitted a beanie so please take whatever I say with a grain of salt...
For decreasing I usually knit 2 together:
Though it might be tough if you want to keep a ribbing pattern.
This method might be the best for you if you want to keep the ribbing pattern all the way up:
Here is a better video on how to do that method for circular knitting:
Hope this helps!