New update: The problems are solved.
First of all thank you two for the attention.
Secondly, I will be telling you what the solutions to each problem were:
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The light textures issue was due to some nodes on my master materials which I created poorly, they were causing some maps to show wrongly. @Get_DOVAH_it I saw the video, but they are different problems, the one of the video was affecting to his movable objects (due to the volumetric lightmap config.) and mine was affecting to the static ones, their lightmaps work different. Thank you anyways
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The shadows of the roof that were projected on other objects were solved by setting the master material to “Two sided”. That makes that any light that comes from outside the spaceship doesn’t cast shadows through the backside of the meshes.