I've always viewed them as different--pensare: to think and credere: to believe. However in English we often use the verb "to think" when we are expressing an opinion, which really means we are saying we believe rather than we think.
"What would be the Italian expression for "We don't think so!" ? Something like "Non pensiamo cosi"?
Why doesn't it accept " Noi non pensiamo"?
It should. Report it.