Hi Jürgen,
There is a lot of back and forth, but we are nog getting closer to anything ;)
I looked at your website, but nothing sticks out that is really wrong to me.
Please understand that plugins provide functionality. The theme creates the layout and styling, like the blue buttons. If every plugin would dictate its own styling, every WordPress website would become a mess.
If you have a preference for a certain background or bold text, could you please be more specific which elements would need which background, and which elements would need bold text?
There is no payment needed for this kind of exchange. If you were only using the free plugin without add-on, this would be fine too.
But you do need to be more specific for me to be able to help you.
Regards,
Marcel