IPhone issues: (Phone not charging right) Anyone got advice?

Okay, so, I have an older phone. I don't know if it matters whether it's old or new, but I have a 6s plus. So, it quit working today. Charging wise, I mean. So my charger quit working with it and I got a new one. First it took an hour to turn back on after dying. Then it got stuck at 1% and would quit charging every few minutes. Then it finally stated charging, but it was still stuck in 1% for a pretty long time. It's now on 38% and seems to be going up, although I'm worried that it's a little slow, but, I can't really tell. Side note, tho: A girl at the store the new charger came from, said that long chargers, which is what I had, tend to burn out faster. I think that might have caused some issues with my phone, but then again I've had this problem with the 6, some Android phones, and some LG tablets. Does anyone know what it could be? I also had to clean my charger port. It had the black gunk stuff in there and was causing black lines on my chargers. I cleaned it out the best I could manage. What do you guys think it could be? I know Apple trends to have a list of issues with phones not charging, so, I'm not going to assume that it's automatically any one thing I come across from googling.

Sounds as if you need a new battery

The problem with all modern technology is that accumulator (battery) gets old and stops storing energy properly. In older models you could just replace a battery, but now they decided that being not able to replace the battery will force people to buy new phones more often. There's nothing you can do ' time to buy a new phone. I have a full drawer of phones where battery does not work properly. There was nothing wrong with the phones otherwise

Is it possible that the rechargeable batteries INSIDE your phone are not holding a charge?

What does this have to do with finance?