NSIS change page subtitle - nsis

Question

I want to support german and english for my setup. German is default.
I replaced MUI_TEXT_COMPONENTS_SUBTITLE for all languages.
For german my replaced subtitle is shown in the exe. But when i change the language in the exe (UMUI_PAGE_MULTILANGUAGE) to english, the standard title (from the nsis language files) is shown.
If i put english to default language my replaced title is shown.
What goes wrong here?
...
!define MUI_TEXT_COMPONENTS_SUBTITLE $(MUI_TEXT_COMPONENTS_SUBTITLE_MY)
...
!insertmacro MUI_RESERVEFILE_INSTALLOPTIONS
!insertmacro UMUI_PAGE_MULTILANGUAGE
!insertmacro MUI_PAGE_COMPONENTS
...
!insertmacro MUI_LANGUAGE "German" ; first language is the default language
!insertmacro MUI_LANGUAGE "English"
LangString MUI_TEXT_COMPONENTS_SUBTITLE_MY ${LANG_GERMAN} "Wählen Sie die Komponenten aus, die Sie installieren möchten."
LangString MUI_TEXT_COMPONENTS_SUBTITLE_MY ${LANG_ENGLISH} "Choose which features you want to install."
...

Answer 1

MUI_TEXT_COMPONENTS_SUBTITLE is not documented anywhere, did you find it directly in the source files?
If you want to modify a single page then you should look at the "Page settings" part of the MUI readme:
!include MUI.nsh
!insertmacro MUI_RESERVEFILE_INSTALLOPTIONS
!insertmacro MUI_PAGE_WELCOME
!define MUI_PAGE_HEADER_SUBTEXT $(MyComponentsSubtitle)
!insertmacro MUI_PAGE_COMPONENTS
!insertmacro MUI_LANGUAGE "German" ; first language is the default language
!insertmacro MUI_LANGUAGE "English"
LangString MyComponentsSubtitle ${LANG_GERMAN} "TEST Wählen Sie die Komponenten aus, die Sie installieren möchten."
LangString MyComponentsSubtitle ${LANG_ENGLISH} "TEST Choose which features you want to install."
Function .onInit
!define MUI_LANGDLL_ALWAYSSHOW
!define MUI_LANGDLL_ALLLANGUAGES
!insertmacro MUI_LANGDLL_DISPLAY
FunctionEnd