AusBonsai

have got like black soot on my port jakson figs dont know what to do ?

Sooty mould is usually a bi product of insects leaving a sticky residue check for scale. If you cant see any I would still spray with confidor. The sooty mould will just wash off once the sticky residue us no longer feedingit.
Cheers
Kirky

Yep, nearly always secondary to scale insects. Look under the leaves, especially near the midrib but you will probably need to look pretty close. They are quite small and usually well camoflaged. Small, brown (sometimes other colored or clear), round and almost flat discs. The insect makes these shells to provide protection while they suck the juices out of the leaves.
Oil based sprays or any of the systemics seem to kill them.