Hi, I’m new here and this is my first post. I didn’t knew how I should title the post, sorry.
Some time ago, I modeled my room, but I had some problems rendering, since, no matter how many samples I would render, the output would still be too dark. But since I had a shitty computer, I tought well, that’s life. But since I got a new computer, I decided to render it again, since I wanna add this to my portfolio. I don’t get if this is a problem with the lightning or what.
This renders have like 5000 samples rendered.
Samples are not meant to effect the brightness of your render, it is only meant to remove noise. Niether will the quality of your computer effect brightness 
There is a very easy way to deal with this problem. Find your scene button (one to the left of your world tab that looks like a cylinder and a sphere) under color management there are sliders for Exposure & Gamma. There is a slider for levels and right above that to the right of “look” (its a little hard to find) there is a new feature that allows you to give your render color profiles out of various camera types.
In addition to that, I find that interiors are brighter and render with a little less noise of you give the room “escape holes” behind the camera. Basically thin rectangles that run from the floor to the ceiling on both sides of the room. This lets the sky light in and the light bounces out. These two things should allow you to bring more light to your scene.
Hope I helped.
Hi! The escape holes helped a lot! But now, I’m getting a real problem of caustic noise and I can’t get how to better it up.
Nice room! You can put an area lamp, make it as big as the wall back the camera and put the same color of the wall in the light, You will have a better illumination. I can recommend You the page www.blenderguru.com, You will find lot of tips there.
I do not have access to your blend so I can’t say for sure. But my first guess is this, never allow illumination to pass through a glass material because it throws a ton of caustic noise. If your window is a glass material, or if your lights on the ceiling are passing through glass than that is more then likely the source of the noise.
You can put a point lamp down the physical lamp too.