Why is the preview render slower than the final render? Firstly, sorry if that's a stupid question. I'm kinda noob :P
The thing is that "normal" rendering with GPU is slower than rendering in preview. I made sure that the resolution in which I render is the same as in the preview but it's still slower as if it was rendered with CPU.
Use rendering CPU to GPU, it can be faster then GPU

Change Render Setting
Use thisenter link description here