Help with my iPhone 8 plus?

Help with my iPhone 8 plus?

Added (1). So I got my iPhone 8 plus from a seller on FaceBook for $250 on February this year. It's a huge upgrade from my iPhone 5s that I was using for 5 years. He said it's only been used for like 2 months.

Added (2). It has little scratches on the screen and a tiny crack on the upper right edge of the phone and it didn't come with the full accessories but it's ok because that's the best offer for an iPhone 8 plus.

Added (3). Everything seems fine and it's really fast and one thing I love about it is the battery capacity. I could use it all day and the battery would be at 60/70%. The only thing I kind of don't understand is the battery health.

Added (4). It's already at 90%. It doesn't quite make sense to me since he told me he only had it for 2 months but he didn't tell me if he got it brand new or from a previous seller.

Added (5). That tiny crack obviously tells me that he has dropped it maybe once. I'm assuming that affected the battery health really bad, didn't it?

If the phone has a crack and scratches on the screen after only 2 months of use that was obviously a rough 2 months, but the drop wouldn't effect the battery. It could have been manufactured a couple of years ago or stored for a long period with no charge, which would easily bring the health to 90%. Regardless for a $250 used iPhone 8 it is what it is. That's what used older model phones are. If you are ending the day with a 50% or more charge you are doing well regardless of whatever artificial number Apple is giving it's "health". In a few years you, like most people will need to get a new battery installed if you keep the phone that long.

Don't worry about that "health" number. If you are getting good battery use, the health number is meaningless.