How do I get rid of these "Shadows" between merged objects

Hello everyone thank you for reading this forum post!

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 things, they are always on the edges of sertiant platforms (See picture 1) and also on some of the walls (See picture 2)
[ATTACH=JSON]{“data-align”:“none”,“data-size”:“full”,“data-tempid”:“temp_156949_1549130942975_30”}[/ATTACH]

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,