11 days is not surprising to have some fermentation still going on, depending on your ferm temp and how long it took the yeast to get going in the first place. If there's still foam on top I would leave it alone for at least a few more days to a week. Of course your only true measure will be hydrometer readings. Check it again in a few days, if the same as your previous reading, your fermentation is complete.
If you give it another week before bottling your beer will be fine. There's no rush to stop the yeast from working on your beer.