Breakdown of Dieser Barkeeper hat den Gin mit Sirup und einer Limette serviert.
ein
a, an (eine)
und
and
haben
to have
dieser
this / that (fem.: diese, neut.: dieses)
Questions & Answers about Dieser Barkeeper hat den Gin mit Sirup und einer Limette serviert.
How could I use schlechthin in this sentence to say he is the 'ultimate' bartender?
You place schlechthin directly after the noun you want to emphasize. To say 'This bartender par excellence...', you would say Dieser Barkeeper schlechthin hat.... You could also emphasize the drink instead: den Gin schlechthin (the ultimate gin).
How do we know the gender of English loanwords like Barkeeper?
English loanwords referring to people or professions ending in '-er' almost always take the masculine article der, following the same pattern as native German nouns like der Lehrer. Because the bartender is the subject of the sentence, it takes the masculine nominative demonstrative Dieser.
After the preposition mit, why does Limette get an article (einer) but Sirup doesn't?
Sirup is being treated as an uncountable mass noun here (like water or sugar), which normally takes a 'zero article' in German just as it does in English. Limette (lime), however, is a specific countable item, so it takes the dative indefinite article einer because it follows the dative preposition mit.
The English translation says 'has served', but could hat serviert also just mean 'served'?