Dell G5 5590 battery problem, cpu and gpu slowed down

Hello,

My laptop has a problem with my battery when plugging in the AC adapter and instead of charging it was plugged in but not charging. I noticed that the flashlight started flashing orange and the battery was only 5% left and stayed there. AC adapter works fine but when I remove the adapter the system turns off.

When I was gaming the system was idle at maximum performance and experienced a very strong lag, the frame rate was severely reduced. CPU and GPU are throttled down. I tried removing the battery then back into the game again and the slowdown persisted

When I open the BIOS screen and run the computer hardware diagnostics and I get:

Battery Information:
Health: Communication Error
AC adapter = 180w

I tried the latest BIOS update, removing the battery and holding down the power button for 10-15 seconds and all the tricks I found on the internet and things still not solved.

I have the following questions:

Do I really need a replacement battery in this case?

Why have I plugged AC adapter and removing the battery, but I can't get maximum performance out of games anymore? Is this problem caused by removing the battery?

Thank you