Hello !
wanted to know, how can we make a sun lighting effect like on the picture ?
i looked everywhere but i didin’t find anything …
can someone please help me ?
Its located in a post process volume 
Ok that does work thanks again 
that effect is called a lens flare. the first link below shows a quick tutorial on enabling it. but the basics are adding a post process volume to your level, then with it selected go to the details panel and look for post process volume, then settings, and then look for lens flare and the options will be there to enable and modify the effects intensity. also if you want it to occur everywhere in the level then set the post process to unbound.
https://docs.unrealengine.com/en-us/Engine/Rendering/PostProcessEffects/LensFlare