Resources folder empty in Build and public variables NullReferenceException

I got 2 big problems that after a lot of research I´m unable to solve.

First problem: I got 5 xml files and a sub-folder inside the Resources folder but when I build my project, the Resources folder is empty (well, only two unity files in there: unity default resources and unity_builtin_extra. So I can´t access my xml files when I do: Resources.Load, anywhere on my code.

I post images to clarify:

Second problem: As Resources file was not working I decided to use public variables for my xml files declaring: public TextAsset myXmlDoc, but I realize that, only when I build this isn´t working as it gets NullReferenceException as if my public TextAsset variable wasn’t assigned by me (wich is not true)

I post images and code to clarify:

public class LoadXml_Narrator : MonoBehaviour {

    NarratorTextClass narratorClass;
    public TextAsset file;

    void Awake()
    {

        print("Xml file " + file);
    }
}

121154-xmlnarrator.png

This is the output log of my Build:

NullReferenceException: Object reference not set to an instance of an object
at LoadXml_Narrator.Awake () [0x0001d] in D:\Projects\PC\Majorel_\Majorel_\Assets\Scripts\XML\Narrator\LoadXml_Narrator.cs:20

(Filename: D:/Projects/PC/Majorel_/Majorel_/Assets/Scripts/XML/Narrator/LoadXml_Narrator.cs Line: 20)

Note: IN the editor everything works
perfect. The issue is only when build
and execute the project.

I found the origin of the problem. I had marked the checkbox: Scripts Only Build at Build Settings. Honestly, I don’t know why becasue I didn’t even know what it does. Anyway thank you so much for pointing me in the right direction. I Was about to go crazy.

After some research I found little info about this option, even the manual doesn´t show it Unity - Manual: Build Settings The documentation just say: Build only the scripts of a project. So I guess it includes only some of the scripts for speed reasons when building.