Just look at the types of each value. That is, the return of:
$objeto_decode = json_decode($objeto);
It will be an object, so to access the attribute contratos, just do $objeto_decode->contratos. However, the type of contract attribute is array, then we must inform the key that indicates which position we desire. If it is the first, just enter the value 0 - if they are all, just go through a loop:
$objeto_decode->contratos[0] // Retorna o primeiro elemento de contratos
But every element of that array is an object that has the attribute negociacoes, then, to access this attribute:
$objeto_decode->contratos[0]->negociacoes
Again, negociacoes is a array of objects that have the attribute parcelas, then we must inform the key that indicates the position we desire:
$objeto_decode->contratos[0]->negociacoes[0]->parcelas
Finally, parcelas will also be a array of objects, then, for example, if you need the value of the first installment, the first negotiation, the first contract, would be:
echo $objeto_decode->contratos[0]->negociacoes[0]->parcelas[0]->valor;
As requested in the comments, to go through all contracts, negotiations and installments, a loop of repetition would be required for each. See an example below:
// Percorre todos os contratos:
foreach ($objeto_decode->contratos as $contrato) {
    // Percorre todas as negociações:
    foreach ($contrato->negociacoes as $negociacao) {
        // Percorre todas as parcelas:
        foreach ($negociacao->parcelas as $parcela) {
            // Código
        }
    }
}
							
							
						 
only one doubt. Using foreach I can use as shown in the image: https://uploaddeimagens.com.br/images/001/080/original/erro.png?1504884435
– Wagner Fillio
I’m getting this mistake:
Message: Trying to get property of non-objectno model. In this line:'id' => $ctt->id,– Wagner Fillio
Your function does not make much sense, tries to review what you have done and understand the problem.
– Woss