Learn Finnish: Ujous ei ole ongelma. - Shyness is not a problem.

Ujous (shyness) comes from the adjective ujo (shy). The standard suffixes for abstract nouns are -uus and -yys. However, because ujo already ends in the vowel -o, adding -uus would create an awkward triple vowel (ujouus). To avoid this, Finnish shortens the suffix to -us for adjectives ending in -o or -ö, giving us ujous.

Why isn't ongelma in the partitive case (ongelmaa) since this is a negative sentence?

This is a common trap! While negative sentences usually force the predicative (the word describing the subject) into the partitive case, there is a major exception: singular, countable nouns. Because an ongelma (problem) is a single, countable thing, it stays in the nominative case here, just like in the sentence Hän ei ole lääkäri (He is not a doctor).

How do I inflect a derived noun like ujous into other cases?

Abstract nouns derived from adjectives have a specific inflection pattern. To find the basic stem, change the final -s to -de- or -te-. For ujous, the stem is ujoude- (so "about shyness" is ujoudesta). For the partitive case, the ending is -tta, making it ujoutta (for example, "I have no shyness" = Minulla ei ole ujoutta).