" recently bought an original battery online and I dont know the authenticity of that battery "
It's a possibilitythe flashing amber/white light means battery is low and isn't being charge. I like to suggest you check the status of the battery and AC adapter in the BIOS.
1. Power off computer, and then make sure AC adapter is connected to computerwell
2. Power on computer, quickly start tapping the F2 key continuously, you should be in the BIOS screen.
Under the main screen, look for the AC adapter type. If the adapter says None or Unknown then it's an issue with the adapter.Suggest you replace AC adapter.
Under the Advanced screen, look forBattery Health, it should say "This Battery Is Performing Normally". If there's any other message, it could mean that the battery is faulty and needsreplacement.
Note: If you indeed needreplacement, please get a new genuine Dell battery thatcomparable with your system.
Studio 1558 Setup Guide- Page 88