Beginner here... What am I doing wrong with lighting/building?


I’m very much a beginner trying to teach myself the ins and outs of Unreal. I followed a tutorial on the learn tab teaching me how to make an office building. I took that and started building something that was recognizable to me (my apartment) and after finishing everything and putting a ceiling to everything I ran into this issue with the lighting. The lines are where the different box brushes are that I used to make the apartment walls. I’m not sure if I’m just lighting something wrong or if I’m building my locations wrong. I spent some time searching trying to find out what was wrong but never quite found the same issue.