Hello, i was trying to fade out a particle fx effect but without success.
There are not opacity sliders eg. on Aura and Dissolve.
They seem only to be switched either on or off.
How could i perform a fadeout, escpecially on Dissolve Melt ?

There are whole lot of parameters for each FX and most of them can be animated at the timeline.
Just play with them until you find right one for your effect.

Aura - Emisson Flux and/or Smoke size.
Dissolve - Reform after melt unchecked + whole lot of other controls below it.

Every time you change any parameter  it creates a key at the timeline (enable Attributes to see what's available and keys)

Your right, i should have tried more options on the Aura.
Smoke Size may help here already.

One thing i fought with was definately the Dissolve Melt.

EDIT: Melt time Duration must be 0 or relatively low to make the Fade slider work on the molten character
depending on the lenght of the whole effect.