It depends on the translator. Some Spanish translations of manga are excellent, while others might have some errors or not capture the nuances perfectly.
The translation of the Monogatari manga is still ongoing, but it's hard to give an exact status. It depends on various factors like the translator's schedule and publisher's plans.
The English translation of the Love Stage manga is satisfactory. It manages to maintain the charm of the story and allows English speakers to engage with the content smoothly. Although it's not perfect, it gets the job done well enough for fans to appreciate the manga in English.