Hello, i am relativ new to Unreal Engine, i am currently in version 5.6. So my problem is that i have created a laser material with emissive color. But the laser lights up the room. Is there a way to fix this? so the laser material does not reflect on other materials? 
Welcome to the forums!
What other light sources do you have in the room? With 15 different sources of that emissive even at 1 that’s going to overpower if your lighting source isn’t balanced but not because of the amount of light but more likely due to auto exposure.
If you open your post process volume in your level and set the metering mode to Manual you’ll get a very different result.
You need to have a decent base level of light, even if you want it to be dark to be able to get what you want out of that emissive material without it completely taking over the lighting of your scene.