Well, there are no softshell turtles in Amazonia. The closest geographically is Apalone spinifera, that reach south of Mexico. But your turtle doesn't give me the impression of an Apalone.
@Great Argus I tought very briefly in said species but the shape, colour and texture of the carapace are wrong, the snout is much thinner and the fore flippers have a different shape, eyes are also much closer/higher and it have the upper lip typical of trionychids and absent in Carettochelys. It's 100% sure a softshell.
