Battery dying quicker on Samsung Galaxy S7?

You might have to replace the battery if it's draining too fast, perhaps there is a problem with the battery hardware wise. That happened to my Sony Xperia Z1 where my battery was swelling up and therefore had to change it. There are video tutorials on YouTube that could teach you how to replace the battery. I believe it should be easy. Or if not and still have warranty, go into a Samsung repair shop..... Otherwise you might have to do some DIY.

Good luck!

Turn down the brightness

That sounds like a typical battery dying problem. As batteries age, they loose their capacity. You can't really "fix" the battery, so it has to be replaced. Unfortunately, the battery is not meant to be user-removable, so you'll either need to dismantle the phone to replace it yourself (not an easy task and is risky) or send it to Samsung or a local cell-phone repair shop.

Bad battery.

Replace.

You have maybe 500 full cycles on a lithium Ion battery. If your phone is say, two years old, you may be reaching this. If so, replace battery.

Another thing to try is fully charge phone, then fully discharge phone. This should teach the circuitry where the charge cycle battery levels are.

Replace the battery.

Your battery is probably around the 80% max capacity so it’s dying much quicker. My iPhone 5s is around the 80% capacity and I get maybe 2 hours at the most before it goes into the recharge zone. When it was brand new, I was getting close to 3 hours.