I took a look at how the letterform G you had as an
.ai file was structured, and found that I agree with @WELZ - it was layered elements on top of one another - all separate.
IMHO this is a non-optimal workflow in Illustrator, as it makes it hard to reproduce things.
My approach to this kind of thing is a bit different: I use the Appearance Palette, add new fills (in this case a white to transparent gradient) and set effects on them (such as Path>Offset with a -0.33 mm offset in this case) and set the appropriate opacity (screen at ~ 33) to get our required effect.
Once I have that prototyped correctly, I save it as a Graphic Style, and then apply that to new elements as I desire:
And in case it's not clear: one nice thing about the graphic style approach is you can apply it to multiple entities simultaneously, and it works pretty well irrespective of specific geometry, provided you've set your offsets correctly: