Masonry is crumbling! Is there a risk of collapse?

It's already a question what exactly one is even seeing here.

Maybe I have a flaw in my vision, but I find it difficult to say based on the picture whether this is even supposed to be the "masonry."

I'm a layperson, but I have seen some older houses that were renovated.
So the question for me would be: is the wall even load-bearing?
What is behind what you see? Is there a proper wall or something load-bearing like [e.g. timber framing]?

It wouldn't be unusual for someone to have slapped something on with whatever means were available. (Due to lack of money or available material).

This is a former exterior wall. So it should be load-bearing. The room behind it is an extension and was used as a laundry room. So far, I have only penetrated about 10cm deep into the "masonry" because I was afraid it would come towards me.

This is a former exterior wall. So it should be load-bearing.

Then there is probably half-timbering somewhere. Do you have the wall "open" on both sides over the entire area? If it is half-timbering, it could also be that you are going through the wrong spot and apart from the "junk" there is nothing, because it is simply filling material.

Then there will definitely be half-timbered construction somewhere. Is the wall "open" on both sides? If it is half-timbered, it could also be that you're going through the wrong spot and apart from the "junk" there's nothing, because it's just filler material.

Yes, I briefly used the hammer drill on the other side, and you could immediately see clay and straw there. However, my wife shouted that I should stop because the side visible in the photo was also crumbling down, and she was afraid for me that it might collapse any moment...

Since then, everything has come to a standstill.

Yes, I can only repeat myself. Maybe the house is even older than you thought (the original house). It was not uncommon for the origin to be a small half-timbered house. The timber frame was often filled with clay and straw. Then over the decades, there were three expansions and often the exterior masonry became interior masonry. Sometimes the wall dimensions no longer align in a straight line and the wall was then filled with whatever was available. That is how demolition material was often reused.

But all of this is just speculation.

I can get you some props and shore it up and open the wall further. Or as you say, then maybe get a professional after all.

Yes, I can only repeat myself. Maybe the house is much older than you thought (the original house). It was not uncommon for the original to be a small half-timbered house. The half-timbering was very often filled with clay and straw. Then, over the decades, it was extended three times and often the exterior masonry became interior masonry. Sometimes the wall dimensions no longer fit in a straight line and the wall was then filled with whatever was available. This is how demolition material was often reused.

But all just speculation.

I can get you some props to prop up and open the wall further. Or as you say, maybe bring in a professional after all.

I will send a photo to my building surveyor and ask him, if necessary he will want to take a look anyway.

Thanks first of all for the help!