UE4 Always Freezes When Building Lighting?

Hi everyone, first time posting here. (Eng is not my 1st lang).

i am currently learning UE4 on a very weak Laptop:
CPU: intel i7 Quad Core @ 2.2 GHz
GPU: Nvidia GT 740m
i know that my laptop doesn’t meet the Minimum System Requirements (like i said i’m only learning the software)
the problem is whenever i build lighting on a high res light map (2048x2048) my laptop freezes although lighting quality is set to Preview, and i don’t encounter that problem when building lighting on the default light map res.

i’m thinking that upgrading my RAM will solve the problem, but if it’s the GPU, then i’ll just have to wait till i buy a high-end desktop PC.

is it my RAM or GPU?

Duplicate post of: UE4 Always Freezes When Building Lighting? - Architectural and Design Visualization - Epic Developer Community Forums