not visible on white solid

I don't speak German, so that aspect will be tricky for me as well.

As a general rule, know that purchasing templates with the intent of altering them can be a very frustrating experience for those without much AE experience. Templates are usually purpose-built to do one thing, and if you start changing pieces without really knowing what you're doing, it can be easy to start accidentally unraveling large chunks of the project (or at least running into walls that you don't even know exist).

The point Rick is making is that it's likely your layer is being ADDED to the other visible layers, both within the Glow effect and possibly on the layer itself. The way color works in programs like this, white is essentially "the most" color you can have, so you can't add anything else to it. If you want the above layer(s) to appear over white, you'll need to change the Blending Mode within the effect:

Try setting it to "Normal" (or the German equivalent).

It's possible the actual layer has a Blending Mode applied as well. At the bottom of the screen, below your Switches column, is this button:

Clicking that will toggle Switches to Modes. If the layer in question is set to anything other than "Normal" (/the German equivalent again, obviously), try setting it to Normal.

Hopefully these will get your layer(s) visible, though they may not look quite the way you're wanting. The ideal here would probably be (re)building this with effects that would work better over white, but hopefully this either gets you close enough or at least helps you see a few options you can play with to get close to the look you're after.

Good luck!