Learn Polish: Nie wiem, czy ten sprzęt jest uszkodzony. - I don't know if this equipment is damaged.

It is the passive adjectival participle of the perfective verb uszkodzić (to damage). To form it, we take the verb stem and add a suffix. Verbs ending in -ić generally take the -ony suffix (often with a slight spelling change in the stem). Because it describes the masculine noun sprzęt in the nominative case, it takes the masculine ending -y, resulting in uszkodzony.

Could we use the imperfective participle uszkadzany here instead?

You could, but it would change the meaning. Uszkadzany comes from the imperfective verb uszkadzać and means "being damaged" (an ongoing process). Uszkodzony comes from the perfective verb uszkodzić and means the action is complete: the equipment is already in a broken state. This perfectly matches the English "is damaged".

Why does the sentence use czy for "if" instead of jeśli?

English uses "if" for two different concepts: conditions and indirect questions. In Polish, you use jeśli for conditions (like "If it rains..."). But when "if" means "whether" (like "I don't know whether..."), you must always use czy.

In English, "equipment" is uncountable. Is sprzęt uncountable in Polish too?