my print results are not as expected

[CVSebastian]

Hi guys, I am currently creating an ad with Affinity Publisher and Photo. Unfortunately the print results are not satisfactory and I don't know what to do. As it looks like there seems to be a problem with the layers. Maybe I am doing something fundamentally wrong when creating the document? 
I have attached some photos to show you where the differences are (even if it is only photographed, you can see the color differences well).

I look forward to your thoughts on this! 

Sebastian 

[mac_heibu]

Looks like the difference between screen colors (RGB) and print colors(CMYK) in combination with a greyish paper color.

Which color profile has your document? Which color definition has, for example, the „red“ of the text?

[CVSebastian]

Thank you mac_heibu. You are right, the color format is CMYK/8, the profile is U.S. Web Coated (SWOP)v2, but the colors are taken from the RGB color space. 
This might explain the problem with the colors. My problem is that our corporate design colors are expressed in RGB, but the printing house needs CMYK. What can I do there? 

In your opinion, does this also explain the problem with the photo used? As the screenshot shows, it is designed to be cut off from the curve, but the print makes it appear again. And why only over the width of the text frame and not over the whole width of the photo (see lower left corner).

 

[CVSebastian]

Unfortunately there is no exact specification, but I'm going to ask for it. They would like it as PDF/X-1a. Do you think there is a problem with exporting? 

What I don't understand either: I have consistently used RGB colors. Then the colors would have to be consistently wrong? How is it possible that the same RGB grey is output differently when printed? 

Thanks for your patience!