How do I get rid of the shadows between aligned merged meshes?

Hello everyone thank you for reading this forum post, I hope you can help me out with a problem I am having with merged meshes.

So I had some shadow problems because they looked a bit “wobbely” and I found out that the problem originated from having a static mesh scaled up too much. So I have split the floor into 16 different pieces which perfectly align with each other and then I merged them into one piece.

But then I saw these two things

So I thought hey did I not allign them correctly, but that wasnt the case. I also tried multiple times to Rebuild the Shadows with different settings but that didnt work either.

I searched around on youtube but could not really find a tutorial telling me how to get rid of this what I believe to be “Shadow”, So I hope someone on the forum can help me out with this.

Thanks a lot in advance I really appriciate the effort!

With kind regards,