RE :If I push the bottom, only small red light turn on few seconds. I thought it might be a battery problem, but it's the same.
Unlike most other drones which can have many batteries to replace when one is out of juice, your L900 has a "built-in" battery. Meaning you have one and only one battery, no backup to interchange.
Here is the question : is it possible that your built-in battery can NOT hold the charge?
If it can not hold the charge, it does not matter how many times you charge the battery, it will lose charge once it is unplugged from the charger.
(I have a drone and I spent dearly to have 4 batteries. 3 years have passed and the batteries will not hold charge anymore. I would charge them and the green light would indicate it's done. I plugged it to the drone, it took off for 5 seconds and it landed. " Out of battery".)
I am electricity illiterate. Please find a drone hobbyist who knows how to test the drone battery.
You will have to remove/unscrew the body case to expose the internal mechanism in order to test the battery. That can be an impossibility by itself.
Until you can be rest assured that the drone's battery is "healthy", no point to consider other means of repair.