svg-points | storing SVG shape data in Javascript | Animation library

I used OpenLayers in Angular2 to show a custom SVG-image as a background map. This works perfectly and I can zoom and scroll across my map.

Now I implemented Features (also svg) and put them all in a seperate Vector-Layer above the map. They are all shown but when I zoom, they get resized weird.

When I zoom out, the Features are getting bigger, when I zoom in the features are getting smaller. I would like to have them always in the same size, so that they are getting smaller when I zoom out (as if it would be static content on the map).

I tried with an extra style-function and experimented by recalculation the scale of the current style of the feature. But I did not get this to work.

So my question ist: How do I put another Layer with Features above an existing layer and when zooming out everything gets smaller?

Am I doing something wrong? Do I need Projections? I am quite new to Openlayers.

Thanks in advance!

A minimal code example, the SVG-Points are getting bigger and bigger when zooming out (same problem at the OL code example: Official Code Example: When Zooming out, the marker gets as big as a whole country or continent....