If you are posting here, and getting steem dollars and steem power, then it can't be a ponzi for you because you are not putting anything in, just receiving rewards for your work. You can convert any steem dollars you receive into local currency right away, but steem power can only be drawn out once a week over a 2 year period.

It takes a few weeks to learn about steemit, but there is a lot of information on here. Read a lot of articles, up vote on a few you like and leave a comment. Use the system and see how it goes for you. Best wishes!