UK
mydomain.com/gb-en- English (default)
mydomain.com/gb-de - German

Germany
mydomain.com/de-de - German (default)
mydomain.com/de-en - English

mydomain.com/gb-en/my-seo-friendly-blog-post - English (default)
mydomain.com/gb-de/my-seo-friendly-blog-post - German

mydomain.com/gb-en/my-seo-friendly-blog-post - English (default)
mydomain.com/gb-de/mein-seo-freundlicher-blogeintrag - German