Hello. How can I remove the amount of fireflies one the windows glass? I have tried to use bigger light source, enable denoising, increase samples, but nothing helped for me. Resolution 1080p shader of the glass upload://y7EKa5CPzZb8bFnuZ7mgyPtnpvU.png
I have tried these, doesn’t help for me.
first, find out (understand) what is the main cause of noise & fireflies in your scene
(hint: emitters &/or glass)
now, try harder
ie. clamp to 1 & set more and more samples… also, replace Glass BSDF for so called fake architectural glass & for the the faster way - introduce AO to the scene
yes, it will take time… either to study Cycles in detail or going the trial&error way
disclaimer
since you share no scene file, i’m out of serving fish on plate
I have setted clamp indirect to 3, clamp direct to 0 and increased samples to 600, i helped to reduce amount of fireflies, but still there are some fireflies.
why stop? don’t you get it now? try with more clamping & more sampling… until satisfied with the result - that’s the trial&error way 
Yea, it is, but how others gets less buterflies with 100-200 sampling 
i can increase clamping, sampling, but it will takes longer to render.
Less light path bounces (up to 3 is fine for the untrained eye, except transmission as it prevents light to go through higher number of transparent surfaces), fake glass & AO (Ambient Occlusion) - main tricks to do it faster for the expense of lighting accuracy 
Well, everything depends on the scene. Some of mine interior I render on 2-5k samples to get results that I like. Now when you know the patter just keep going. And what @burnin said - some nice trick to help you with render time.
Separate rendering with environment and rendering with interior lights and add them together.
Also, use as big light sources as possible - make the shade the actual light source instead of the bulb inside (can be removed) if that is how you set it up.
Indirect lighting is extremely prone to noise. I tend to help out mine using some global AO. Only suitable if you don’t want dark corners.
Without a scene it’s really hard to guess.