Show content that is tagged to both current node and translation source
The problem isn't getting both the source and translation nodes into Views results, that's easily done. 

The problem is when you apply the Contextual filter. Because the plain Entity reference field Contextual filter isn't translation aware.   

But you can make it aware of translations with the help of the Relationship Content translation: Translations. 

I don't know if your filter for Media to be in English will cause any trouble, so try to remove it if you see any problems. 

Also as far as I can see you don't need the Entity Reference: Application Ref Relationship, you're not using it in any of the Fields and unless you need it for something not visible here you can safely remove it. 

List nodes referencing a node, along with nodes referencing its translations

Here are the steps you need to do on your Views to make it Contextually sensitive to not only the referenced entity, but also to that entity's translations: 


You already have Training materials views showing some fields.  

Don't include any language filters, unless you plan on allowing all the languages which defeats the filter's purpose anyway. 
Add the Content translation: Translations Relationship and configure it:
Don't Require it (although I haven't noticed any difference)
Translation option: All 
Add the Content: Application Ref Contextual filter and configure it:
Use the Translation Relationship!
When the filter value is NOT in the URL
[whatever you like, All results or Default Content ID from URL]
When the filter value IS in the URL or a default is provided
Specify validation criteria
Content
Application
Node ID


Now if you enter an Application node ID of any language, you will see all Training nodes referencing it AND all Training nodes referencing translations of the Application node.