Sometimes you may be asked at the time you take your shahada if you also believe in other things for example Angels, other Prophets, and the Day of Judgement.
You may not yet be sure on your belief in these matters.
It may take time for some new Muslims (particular those coming from a no faith background) to understand these, and are often internalised further along on their journey. Keep an open mind to the other articles of faith, but realise they are not a pre-condition to embracing Islam. The key at this stage is that you feel comfortable in acknowledging your belief in the two declarations of faith.