Learn Turkish: Son ödeme cuma günü. - The last payment is on Friday.

Not all verbs take the -(I)m suffix to form abstract nouns. While we have seçim (from seçmek) and ölüm (from ölmek), the verb ödemek (to pay) uses the standard verbal noun suffix -mA to create ödeme (payment). By coincidence, the word ödem does exist in Turkish, but it's a medical term for "edema" (swelling) borrowed from French!

Why is it cuma günü (Friday's day) instead of just cuma?

When talking about days of the week, Turkish speakers frequently use a noun compound structure: the name of the day plus gün (day) combined with the possessive suffix -ü. While you can simply say cuma, using cuma günü is extremely common and sounds very natural when specifying the day an event or deadline occurs.

English uses the preposition "on" for days (on Friday). Why isn't there a locative suffix (-de) on günü?

Turkish usually doesn't use the locative suffix (-da / -de) with days of the week to say "on" a certain day. Just stating the day, like cuma or cuma günü, acts as an adverb of time all on its own. Adding -de is not grammatically required and is usually left out.