This is an irregular verb. It follows the conjugation pattern of the verb ter.
Conditional:
(Eu) obteria um reembolso se o produto tivesse defeito.
I would obtain a refund if the product had a defect.
Present Subjunctive:
É importante que (eles) obtenham todos os documentos hoje.
It's important that they obtain all the documents today.
Preterite:
Nós obtivemos as permissões necessárias.
Obtivemos as licenças necessárias.
We obtained the necessary permits.