Hi @Lili Ivany 

There is not OOTB process to do it. But yes it is possible by doing the custom logic.

1. When we change the language from the profile of the Portal then it is converted from the system property. The only way we can get the value from it by doing the script "gs.getSession().getLanguage()".

2. The custom logic for this is, You just need to create the custom field on the user profile "Portal Language".  

3. You need to set the custom field with the same language selected on the Portal. And it should be set when the language is changing. By default, you have to run the fix script on the User Profile to set the field the first time.

4. For the Notification part you have to create the Notifications in the different languages and apply the condition that "User >> Portal Language >> English", "User >> Portal Language >> German".

For any coding assistance required for this please let me know,

Mark correct/helpfull if this helps your query. 

Thanks,

Ankur Swami