Do not rename resources.resx: instead, just add resource files for the additional cultures that you need.
Resources.resx contains “neutral” resources that will be compiled into your main assembly and used as a reserve if the satellite assembly for the required culture is not assembled.
Each additional resource file, for example. Resource.fa-IR.resx will usually be compiled into a satellite assembly related to culture.
You can also add to AssemblyInfo.cs NeutralResourcesLanguageAttribute, which tells the ResourceManager of the language you used for neutral resources:
assembly: [System.Resources.NeutralResourcesLanguage("en-US")]