Did people always think that the earth was round and that the sun was in the middle of the solar system?

Always? No. Some people thought the Earth was a disk held up by four elephants on the back of a giant turtle (a motiv adpoted by a popular science-fiction/fantasy series). Aristarchos of Samos published the first heliocentric model, but it was centuries before the so-called Copernican theory was generally accepted.