serious challenge

Translations
серьёзное испытание
непростая задача
серьёзный вызов
серьёзная проблема
Definitions
A difficult or demanding task or situation.
A significant test of someone’s abilities, determination, or resources.
A formidable problem or obstacle that requires substantial effort to overcome.
Words
serious

adjective
серьезный
challenge

noun
вызов