I have downloaded a file of a site plan and for some reason its on different layers in a 3D model  and i need it in 2D as i need some measurements. I do not mean layers as in working layers. Is there a way how to merge them into one layer? 

Hello calmer, I do suppose that you want to set to Z=zero all the entities of your drawing.Then try and use the command FLATTEN and take a look at a 3D point of view like LEFT for example to see if all is OK.Do it on a copy of your file for safety, see if any layer are frozen etc...

calmer: You mean the entities have different ELEVATIONS don't you?
John Connor2016-04-26 11:42:14

Thanks I got it fixed by bringing all groups set to Z=0.