Here is a musical glossary of German terms based on The AB Guide to Music Theory (Part 1), by Eric Taylor¹. These are terms which you’ll often see in 19^th century Romantic music written by German composers, such as Fanny Mendelssohn.

Term	Symbol (if appropriate)	Definition
aber		but
als		than
am Frosch		use the bow of a string instrument at the heel, ie the end held by the player
an der Spitze		use the bow of a string instrument at the point, ie the end opposite to that held by the player
Ausdruck		expression
bestimmt		with decision, definite
bewegt		with movement, agitated
breit		broad, expansive
Dampfer		mute
doch		however, yet
ein		a
einfach		simple
Empfindung		emotion, feeling
etwas		somewhat, rather
feurig		fiery
Flatterzunge	Flzg.	flutter-tonguing, a direction for wood-wind instruments
frei		free
frisch		vigorous
frohlich		cheerful, joyful
gebunden		joined
gehend		at a stead speed, equivalent to andante
gesangvoll		in a singing style, equivalent to cantabile
geschwind		quick
immer		always
innig		heartfelt, sincere
kraftig		strong
langsam		slow, equivalent to adagio and lento
lebhaft		lively, equivalent to vivace
Leid		grief, pain
Leidenschaft		passion
leise		soft, gentle
lieblich		lovely
lustig		cheerful
massig		at a moderate speed
mit		with
munter		lively
nach und nach		gradually
nicht		not
noch		still, yet
ohne		without
rasch		quick
ruhig		peaceful
schleppen, schleppend		dragging
schnell		fast
schwach		weak
sehr		very
stark		strong
suss		sweet
traurig		sad
und		and
viel		much
voll		full
vorgetragen		brought out, prominent
wenig		little
wieder		again
zart		tender, delicate
ziemlich		moderately
zu		to, too

References:

1. The AB Guide to Music Theory, Part I – Taylor, Eric (abrsm.org)