Is 30 minutes enough time for a swedish massage?

It all depends on your reasons for going for the massage and the areas you want treating. For a back massage, 30-45 minutes is a good amount of time to give a thorough massage to the shoulders, neck and lower back. For work on other specific areas, then 30 minutes ona regular basis should be enough.
For a full body Swedish massage, I would recommend a minumum of 60 minutes and anything up to 90 minutes. For your first treatment I would suggest a full body massage, that way, the therapist can locate areas that may need more attention during future treatments.

A 30 minute Swedish massage would not be sufficent time for a full body massage. it would be great for a back and should massage or to work on an other specific area.

30 minutes is enough only for treat some particular areas and not for the full body.