It is unknown how much uranium they have enriched to 90%, but the IAEA have confirmed that at least 280kg have been enriched to 60%, and Iran is producing an additional 9kg per month from these facilities. I’m not overly familiar with how long the enrichment process will take to go from 60% to 90%, or even if it is a different process than their existing one.
But the jump from having sufficient materiel to having a functional physics package is extremely short and not at all complex - it’s taught in AP Physics classes and well described on wikipedia.
Point being that they are potentially mere months away from having nuclear weapons.