Why is the volume scatter more dense in the viewport than in my final render? I need to get the same effect as in the viewport, but I can't find a difference in the settings for viewport and final render. All lights are render-activated in the outliner, and in the object properties. Thanks for any help

 (I changed the green color a little, so it's not 100% as in the images provided)
You can try setup like below. 

Then adjust "density" and mix shader fac.
Then what You also can do is to power up your lights.