This is the 8918th most frequent German word.
langsam
Slow.
In this sentence, 'langsam' is used as an adverb to describe the manner in which the car is driving.
Das Auto fährt langsam.
The car drives slowly.
Here, 'langsam' is used in the comparative form ('langsamer') as an adverb to indicate the manner of speaking.
Bitte sprich langsamer.
Please speak more slowly.
In this case, 'langsam' is used as an adjective to describe the 'Service' as slow.