"1- render outputs don't look clear1 it always has noise"
If it's not clear, the resolution is probably too low. If it has noise, there's not much you can do, but just need to let it render more hours. You need a strong CPU.. Or maybe you can read on Corona help website for some optimizations. But you shouldn't change render settings as those have almost no impact on render times.
"2- VFB disappeared" - this one is not very clear. Maybe you can post some pictures for problem nr 1 and 2, so you'll be able to get better help.