I was convinced it should be plural because the accusative singular would be "golarkę". Turns out that "potrzebuję" takes the genitive (see https://en.wiktionary.org/wiki/potrzebowa%C4%87) so "golarki" is genitive singular rather than accusative plural. But unless I've missed some explanation, this wasn't made terribly obvious here.
I agree it's not very obvious, although I remember a discussion in an earlier lesson mentioning that potrzebuję takes the genitive. Perhaps it's easier to remember if you translate potrzebuję as "I am in need of" rather than "I need"
Another aide-memoire / pons asinorum I have seen is that you could consider it as being similar to the genitive that is used in negative sentences; if you need something it's because you don't have it -- Nie mam golarki, potrzebuję golarki.
So what does one say in Polish if you need more than one razor? What is plural genitive?
"golarek" (declension here)
You can also find the name "maszynka do golenia" (little machine for shaving) - although it's a lot longer, it's in normal use and for example I'd be more likely to use that than 'golarka'. "Maszynka" itself could probably be understood to mean the same, although that's only 'probably'.
Hmmm... "Potrzebuję golenia", although that sounds as if you are about to go to the barber (?) and have a shave, which is rather uncommon nowadays.
"Muszę się ogolić", I would say (I have to shave). With perfective "ogolić" because the result is important and not the process.
"Chciałbym" for a man and "Chciałabym" for a lady (nevermind the context here). It's like "I would want", only that's rather not what you'd say in English.
As the conditional forms are built on past tense forms, they show the gender of the subject.
No no no. That would be like "I would like I drink coffee". It wouldn't make sense.
Well, with words you know, you could write "Chciałbym pić kawę", which would be "I would like to drink coffee" - but it'd sound as... if you wanted to spend your life drinking coffee? as if you wanted to drink coffee for a living?
You should use one of the perfective equivalents here. So either you have "Chciałbym wypić kawę" (I'd like to drink the whole cup/mug/whatever of coffee) or "Chciałbym napić się kawy" (with Genitive), as in "I would like to drink (a bit/some) coffee).