fungus gnat

Cure for this used to be a drop or two of malathion in a little water, watered into the compost - but I don't know if malathion is still available, might have been withdrawn.

There are specific "fungus gnat" sprays for houseplants that you can get.
You can also try scraping off the top layer of soil down to at least 1/2" and replacing it with fresh soil.
Try not to overwater the plant as fungus gnats love moisture.
The other thing that I find is really helpful is putting those little yellow sticky cards in and around the plants. You'll be amazed at how many gnats they catch and they will help lower the number of gnats.

Thanks for the answer.I found out last night after serching on internet sprinkle ground cinnamon over the soil in the pot.I try it last night and looks like the flyes gone,but not sure if left any of them in the pot.

Cinnamon - great, I'll try that, much more natural for a start.