Mid making help plz

[hellhound95]

Hi not sure if Iâm in the right place but why not start here. So I have been trying to make alterations to my player home I was adding a hallway to stork different power armor suits in So I got it put together didnât add any lighting or anything just the hallway so I try test playing it and I can walk in it to the end no problem but when I walk in it the back half of the hallway is just white light but when I walk into it then it comes to how can I fix this issue new to this whole mod making