Would replace the battery but:

try letting the laptop die completely Like playing a 4 hour long video at 4K, then when it kills itself hold the power button for 5 seconds and then unscrew the bottom panel. Use suction cups to remove it. Then disconnect the battery and hold the power button for 15 seconds. Then plug it back into the system the battery and then hold the power button again for 10 seconds. Then let the laptop charge and then check if it charges again.

 

Wifi issues can be resolved in the device manager by manually switching the speeds.

https://www.thewindowsclub.com/switch-between-2-4-ghz-and-5-ghz-wi-fi-bands

Hi @Mr. stark  welcome to this user to user discussion forum. This is not Dell Support. 

For the typical user, noticeable reduction in Battery run time will generally be observed after 18 to 24 months. For a power user, reduction in run time generally may be experienced within 18 months. Dell recommends buying a new replacement OEM laptop battery when the run time does not meet your needs. 

Although BIOS says battery working normally, your laptop function requires power from the ac adapter. Battery health deteriorated by almost 50% requires further investigation. Please create a Windows 10 Battery Report and look at (1) full charge capacity compared to battery design capacity, and (2) battery life estimate. Postulate that this will confirm your suspicion and laptop's behaviour, that the battery should be replaced. 

Laptop without battery is designed to function as Desktop on ac adapter power. This will provide time to get replacement battery.

Please note that getting a non-OEM battery is false economy and usually will not be charged. Getting a good new replacement OEM battery is now difficult, on delivery check the white label DP/N code and the year/month date beneath the square matrix should be less than 6 months old. 

Storing a dead battery in the laptop is not recommended because battery chemistry will continue to degrade the battery, and swollen Lithium-ion batteries are a safety hazard to both you and the laptop. 

Please click on Kudos to say thank you for response from user that is not employed by Dell. Please share an update on progress, so that other users derive benefit from your experience. Thank you. 

Hi @Mr. stark  user Ashok Jaiswal found a solution Here. Ashok tried to use Dell Mobile Connect (DMC) on Dell Laptop but it never worked with OnePlus. 

What Ashok did was to unpair my laptop from phone's BT list and unpair phone from my laptops BT paired list. Post that Ashok left both my phone's and laptop's Bluetooth on. Ashok left the DMC application on in my laptop where the code was being asked.

In the background Ashok went on my windows settings and tried to pair the phone using Microsoft's your phone app. Once paired, the application will allow you to see messages and photos but to use the call feature on laptop it will try connecting with Bluetooth again. Once paired the your phone app will show an error that an application installed by the manufacturer is preventing it.

That is when you open the DMC app on your phone and it will display the code. And you can use it to login on the DMC app on your laptop and everything will be in place. 

It worked for Ashok. Hope it helps you too.