Is this a decent starter bike?

1.) I would practice shifting first. You will almost never use the largest Chainring ( the big front sprocket). A lot of people remove them and install a bash guard in place of it. You don't need to do this. Just shift between the lowest (smallest in front) and the middle chainrings. In the back, your Cassette ( cluster of sprockets), the Lowest is the largest sprocket. The easiest (quickest) way to adjust for a hill is to shift your front derailleur (left thumb) to the smallest chainring. When you head downhill or are on a flat dirt trail, you shift the front to the middle chainring. Use your right thumb (rear derailleur) to make micro adjustments in either condition. Try to keep a fast enough cadence that you are spinning, but not so fast that you are bobbing. Not to slow where you feel like you are pushing from side to side.
2.) Practice braking. Braking is very important and takes a long time to get the feel for. You don't just grab both levers. If you do, you'll end up going over the handlebars. The front brake ( the left lever) is very powerful and quick to engage. The back (right lever) is more forgiving. If you squeeze the back to hard, you will just skid the back tire. I can always tell an inexperienced rider by the wear on their back tire. You use mostly back brake with a percent of front brake. You feather your brakes, meaning you squeeze them progressively till you have enough braking force to stop your bike. On steeper downhills or situations that you need to stop quickly, move your body backwards off the seat as you brake harder. The harder you brake, the further off the back of the seat you will need to be. This is why we use Dropper seat posts. A seat post that drops with the push of a lever on your handle bars. If we go down steep hills we lower our seats so we can move way back over our rear tires to counter balance the intense braking force that wants to throw us over the bars. You may want cheap one on your new Kona at some point?
Have fun.....