Forge map problem

hello, recently i spent some days workin on a map, my first creation, not really impressive, but pretty proud of it as it is my first map. however, as the map took lot of blocks (its a remake of a map from another game), it show to have some lightning issues, like all the shadings for walls, ceilings, floor are ok, but some objects just have an ultra black color and i dont know how to fix it. some parts of the map also seems like ‘glitchin’, you that effect when two blocks are merged into another (happen on a part of the ceiling) and it seems like it move? let me know if anyone is able to help me in someway. thanks