Dell inspiron 5555 battery charger issue

I bought the laptop from a guy I know and the PC is just 3 months old. But from the first day I got it I've been facing problems. I managed to get all the software problems fixed (Firewall detecting viruses where there were none, all my files turning into files of size 888kb, driver problems) but now another problem has come up.

Before yesterday it always seems like I have to press the power button twice before it turns on. Yesterday afternoon I pressed the power button twice and it didn't turn on, then I plugged it in and it turned on, and the battery was full. I removed the charger and it was still working so I don't know why it didn't turn on at first.

Later in the evening as usual I went to this place to use the WiFi there and after downloading some stuff I hibernated it and went back to my dorm room. Only to turn it on and be told that 'my battery is critically low' which shouldn't be so because I was charging it while browsing and the battery was at 100%. So I plugged in the charger and pressed continue, and all of a sudden caps lock and the battery symbol started to blink. The battery symbol was blinking white and off (with orange randomly blinking in between) and the caps lock light was blinking steadily. When I tried to type my password (my laptop password is 'anonymous') the keyboard seemed to be malfunctioning because it typed something like 'a$&@+nonyidjdjdjmous' , like, basically strange characters in between my password. So I shut it down and the lights stopped blinking, it stayed white like it was charging. Then I removed the charger but it still stayed white!

I then removed the battery, and just went to sleep ***, hoping it would work later. I woke up around 6AM this morning and tried it (plugged in) and the caps lock kept blinking and this time the battery symbol was blinking steadily (white, off, orange, off, white, off, orange. . .) but when I got to the lock screen the keyboard didn't malfunction anymore. My PC showed that the battery was almost empty, and 'plugged in, not charging'. I removed the battery and it was still working while showing plugged in, no battery detected (which was what I expected). Meanwhile the caps lock and the battery symbol hadn't stopped blinking all through this. I felt uncomfortable with it blinking like that so I just switched it off. I tried switching it on again, still blinking, so I long pressed the power button to turn it off. Then this is where it got weird. When I'd long press to switch it off, the battery would stop blinking and stay on white. Then as soon as I unplug the charger they keyboard would light up and it'd turn on by itself (its supposed to be off). That kept happening so I turned everything off and just left the PC alone.

I tried to be as detailed as possible so you'd have all the information if you could possibly help me out with a solution. I kind of feel scammed now sort of because the friend I bought it from has sold me a bad phone in the past but he claimed he didn't know so I trusted him and overlooked it. I'm starting to feel like he knew his PC was a disaster waiting to happen. But, I didn't think he could be lying because I was there when he first bought the PC and I saw him unbox it.

P.S, I had looked on the internet for other solutions and I saw somewhere where it says the blinking latter could be because of an unsupported charger but the charger I'm using is the one that came with it. .