The Geman word for “to serve” is “dienen”. Note that the word “servieren” is only used for serving food. From “dienen” we also get “Diener” (m.) for “servant”, and “Dienst” (m.) or “Dienstleistung” (f.) for “service” (the former more in the sense of “duty” or “employment”, e.g. in the military):

– “Ich bin bereit zu dienen.” – “I am ready to serve.”
– “Womit kann ich dienen?” – essentially “What can I do for you?”
– “Sie dient ihrem Lande.” – “She serves her country.”
– “Das Abendessen ist serviert!” – “Dinner is served!”
– “Er ist ein zuverlässiger Diener.” – “He’s a reliable servant.”
– “Ich habe Dienst.” – “I am on duty.”
– “Er ist auf einer Dienstreise.” – “He’s on a business trip.”
– “Das sind unsere angebotenen Dienstleistungen.” – “These are our services offered.”

As an interesting note, “einen Diener machen” (literally “to make a servant”) is a German expression for “to make a bow” (as in, to bend the head).