Goodmorning Ernest. I am sorry. Yesterday I was so tired that I completely forgot what I wanted to achieve in the first place with this search field. Your original code is working perfectly. In the excluded array, when I put my custom post type it indeed excludes attachments from it. That was my goal. So thank you for your help.
If you could answer also the question, how I can limit this code only to this search instance and not let it affect future ones, that would be great. Thanks 🙂