Translation:I am looking for a person who is a client of this company.
Why isn't it osobę? Is it only because the verb szukać requires always genitive and never accusative?
Yes, that is the reason. I advice you to google "szukam osobę". There are few thousands of occurrences. Many people make mistake and use szukam with accusative.
These are adjectival participles and as such they decline.
Nominative -> genitive:
ta osoba będąca -> tej osoby będącej
ten mężczyzna będący -> tego mężczyzny będącego
to dziecko będące -> tego dziecka będącego
ci mężczyźni będący -> tych mężczyzn będących
te kobiety będące -> tych kobiet będących
That explains it well! Thanks! One question, though: singular masculine będący is the same as the plural masculine będący. Does personal/non-personal make a difference?
pies będący? psy będące?
I completely forgot about this. Yes, it makes a difference. As a native speaker I often think that there are only 3 singular grammatical genders.
ten człowiek będący -> ci ludzie będący, personal
ten pies będący -> te psy będące, non-personal animate
ten komputer będący -> te komputery będące, non-personal inanimate
Is there an example where pies/psy (animate) and komputer/komputery (inanimate) are different, other than declining in genitive?
doesn't "beda" mean will be? I put "I am looking for a person who will be a customer for this company" wouldn't that make more sense?
Duolingo is trying to teach a specific tense, so the analogous English construction makes it easier to understand. Simplifying the tense doesn't help to learn the Polish