Ok I have 4 raw files that i import to my map and the seaming dont work on unreal for some reason, its always worked when i imported tiled landscapes. is there a way to export my land as heightmaps then re import them as tiled landscapes
You can do that with the gizmo tool -> https://docs.unrealengine/latest/INT/Engine/Landscape/Editing/Gizmos/index.html#gizmodataimport/export 
I need to export the heightmap from unreal engine and edit it a bit in blender, so how to export height map as PNG?
Have you ever tried selecting the entirety of a large map tile with that tool? I’ve not found a way to do that. All the instructions seem focused on copying only portions of the map.