Noise eveywhere

Hi everyone!
Faced with a problem, when im changing in “light paths” menu Limited global illumination to Full global illumination
i have so much noise on my pic. I changed Diffuse value from 128 to smthing like 15 or even 5, it worked but i don’t think that value should be changed for getting realistic pic. Pls help me to fix that and figure out why am i getting so much RED NOISE.