It is not natural. By using three past participles you have created a sentence that is overly passive and creates many unanswered questions: Who gives? Who supposes? Who does not delay? The sentence contains no verb except "to be" ("are" and "is"). That verb doesn't actually say anything since all it does is introduce two adjectives ("given" and "supposed"). Without verbs, sentences feel dead. They contain no action. They make no assertion. It is not possible to communicate effectively using only adjectives. Here are ways to say the same thing using verbs: "When someone gives you a task, they expect you to not delay." (verbs: "give", "expect") "When you have responsibility for a task, you should not delay" (verbs: "have", "should delay") It's OK to use past participles. Just don't rely on them exclusively: "When you've been assigned to a task, do not suppose that you may delay doing it.

When you’re given a task, it is not supposed to be delayed The above change sounds perfectly fine grammatically, but might be a bit of an odd sentence by itself depending on the situation / what you want to communicate

When you are given a task don’t delay it.