If
urbanplantswoman could get some more diagnostic images, this could be solved. If possible, take some close clear images of the leaves showing arrangement along the stems, some clear closeups of those fat dormant buds, and some pictures up inside that crown that is entirely hidden in these pictures - which could show whether this is a top grafted plant or whether it has just had regular crown pruning to create the density/shape.
To me, this has
alternate arrangement of simple leaves - evidenced in image #2, as opposed to the opposite arrangement mentioned by the original poster.
I agree with
Liquidambar sp. identity, and suspect it is a clone from a southern seed source in its native North America. The leaves fit; the buds shown in image #2 fit.
As for the evergreen-ness and/or lack of decent fall color expression: Southern/warmer provenance plants - when grown in colder/more northerly conditions - often do not have enough of a growing season to complete their normal cycle of outstanding fall color before shedding leaves and going dormant. Add to that the location in northern Bavaria (Germany is not well known to provide excessive numbers of hot sunny days to replicate from whence American Sweetgum hails), and it adds up to what is depicted - leaves freezing/dropping off green (image #3).
There are innumerable
Pyrus calleryana planted and grown in my part of the world. It is not uncommon at all for leaves on these trees to freeze green on trees. About once in 3-5 years is the season long enough (or frosts/freezes hold off) for the full blown fall color to be expressed. There are many clones that have been propagated, and you can easily compare performance of a 'Bradford' versus 'Aristocrat', and a dozen others.
There are also at least 3 named diminutive and globular
Liquidambar styraciflua clones: 'Gumball', 'Lollipop', 'Oconee' are three. Descriptions from noted authors point to lack of hardiness (especially in northerly conditions), but beautiful fall color when grown in its native haunts.
That plant just needs to take a vacation to the south of France...