Since you say the "light takes over the picture," I'm guessing that what you WANT is for the picture to be darker overall, with mostly the lights of the tree showing up, right?
With fully auto settings, the camera is trying to correctly expose the entire frame, and that ends up making it brighter than you want. Here are some things you can try:
When you have the camera app open, touch the settings icon at the top (looks like a little gear wheel). First make sure your flash is turned off, then try one or more of these options under settings:
1. touch "Exposure value" and then move the slider to the left to make the overall image darker than what the camera would otherwise select;
2. touch ISO and change it from Auto to 100, the slowest sensitivity for the camera sensor;
3. if the above changes don't get you what you want, touch Metering and change to "Spot" which means the exposure will be measured off a particular spot that you select in the frame. You can touch the screen to move that spot (a square) around from dark to light places in the frame, to hopefully get the exposure you want.
Play with these settings, and you'll have a better chance of getting the results you want.