>>"handy" is a cell phone, an "evergreen" is an old well-loved song, and an "oldtimer" is a vintage car<<

These words exist in English usage with the same meanings, so I guess the cross-over to German was fairly predictable.

Similar things happen here in New Zealand, where Maori words are commonly interspersed in English speech. I have heard them in Radio and TV newscasts, so they must be acceptable. But then I have also heard some of the most excruciating verbification of nouns in the same media, so New Zealand English can't be held up as a paragon of linguistic virtue!