will that LED be very bright? I want something that is so bright its visible in daylight. or at least extremely bright at night. The light i have now is barely visible if i'm near any street lights
Yeah, you'll blind yourself looking directly into it too long. Its bright. Be sure to heat sink it WELL. If it gets too hot, you can ignite the head liner. So if possible, remove the liner where the light assembly will go, and use the roof as the heatsink.
The trouble with buying low quality items from "that country" is that there is no detailed datasheet like the datasheets for American Lumileds. You will need a heatsink for each high power LED. It has some kind of base that can be bolted to a heatsink.
If you put it in a plastic box in a door panel, you will probably wind up with freshly fried LEDs.
If you can attach the LED mount to the steel of the door frame, that might pull enough heat away from it. Steel really isn't a wonderful conductor of heat, though. Aluminum is far better. Copper is nearly twice as good as aluminum. Water is much better than copper.
People routinely leave car doors open for extended periods of time while they are cleaning the interior, loading/unloading lots of items, and/or performing maintenance.
If you are going to skimp on the heat sinking, you better have a way to automatically turn the LEDs off after a period of time.
You should consider having a timer in there which will cut off the light after the door has been open for a period of time, say 30 seconds to 3 minutes.
I would not be happy if a light drained my battery.