"I think it's not possible."
Translation:Yo pienso que no es posible.
Pensar and creer are pretty much interchangeable as 'to think'. But creer also means to believe.
Why is que in the translation? There is no "that" in the english sentence
Actually there is. It is just not there. Optional in english mandatory in spanish
The subjunctive is triggered if you say "no creo que" but not if you say "creo que". It's a Quirk of Spanish and it works the same with pensar.
Should that not read I don't think it is possible? I don't think I ever heard anyone say I think it's not possible. Maybe that is just me.