In fairness, (and agreement with marto) you do not look to have put much effort in so far. You need to look into books or web sites which show good database design. No one in their right mind would create a table with 600 columns, one per answer.

As a start, think of the data you need to store and divide it up into relational tables. e.g., a table users storing a username and id, one storing questions and question id, one storing all possible answers and answer ids, and one answers storing user ids, question ids and answer ids. You have the state of answered questions for a user at any time by looking into the rows written into the answers table.

However there are many possible ways of doing this as your research will lead you to find.