Learn Turkish: Kazanç düştüğü oranda asgari giderler bile sorun olur. - To the extent that earnings fall, even minimum expenses become a problem.

We use the verb düşmek (to fall) + the -dIk participle + the 3rd person singular possessive suffix -ü, resulting in düştüğü. We then add oranda (at the rate / in the proportion). Literally, it translates to "at the proportion of its falling." This is the standard pattern for expressing "in proportion to [verb]ing" or "to the extent that [verb] happens."

Why doesn't kazanç have a genitive suffix (like kazancın düştüğü oranda)?

When stating a general rule about an indefinite or non-specific noun (earnings in general, rather than "the earnings of this specific company"), the subject of the -dIk clause often stays in the bare nominative case. However, the verb still requires the possessive suffix (-ü in düştüğü) to complete the clause structure.

Could we use ölçüde instead of oranda in this sentence?

Yes, absolutely. Düştüğü ölçüde (to the measure/extent that it falls) and düştüğü oranda (at the rate/proportion that it falls) are practically interchangeable here. Oran literally means "ratio" or "proportion," while ölçü means "measure."

Giderler means "expenses," but does it come from the verb gitmek (to go)?