I do have the problem I want to access the messages from the en_us.lang File
I am using  1.11.2 - 13.20.0.2296
 

I am trying something like:

 

if(!Init.isInitialized()) {
    Language currentLanguage = Minecraft.getMinecraft().getLanguageManager().getCurrentLanguage();
    ResourceLocation loc = new ResourceLocation(MODID, String.format("%s.%s", currentLanguage.getLanguageCode(), "lang"));
    InputStream resourceInputStream = Minecraft.getMinecraft().getResourceManager().getResource(loc).getInputStream();
    Init.init();
    //Init.fileInit(resourceInputStream); This is not possible because it has private access
}

//This is what I want to do to replace the tooltip with a description I defined for the item
description = I18n.translate(this.getUnlocalizedName() + SurviveThis.DESC_SUFFIX);

 

I am stuck. Google does not help me .... 

What are you even doing? You can access anything in the language files using I18n.format. Be sure to use the net.minecraft.client.resources.I18n class, instead of the other 2.

It not documented anywhere I just imported the wrong.