A Feature Level 5 video card is required to run the editor.AvaliableFeatureLevel = SM4, ShaderPlatform = PCD3D_SM4,and because of this I cant start engine?
What’s the video card in your machine?
If I remember correctly, it’s possible to run in the older SM4, but you’ll lose access to a bunch of features.
1gb not 512mb but it is same 
ATI Radeon HD 4600
This is a 10 year old card with no DX11 support and simply does not meet the minimum requirements.
You’re most likely sitting on 512MB or vram, too which will make the experience pretty unpredictable.
Even if you somehow manage to run the editor, you’ll be unable to accomplish much.
It seems that the support was dropped completely during last update - 4.18
Deprecating support for the Editor running in Shader Model 4
This release we will be deprecating support for running the Editor while using Shader Model 4. This mainly affects users with only DirectX 10 capable graphics cards. Starting on the next release we will require a Shader Model 5 (DirectX 11/OpenGL4/Vulkan) capable card.
Find the editor UE4Editor.exe file in Program Files\Epic Games\UE_4.19\Engine\Binaries\Win64
Create a shortcut, go to its properties and add -opengl
Now, most importantly, grab a cookie and a cup of something good cause it’s gonna take a while…
If this does not work, consider installing one of the previous versions of the engine.
Good luck.
ATI Radeon HD 4600