My grandmother and my father speak the language of Asgard. Suzume is almost fluent in it too. I would ask either of the women if they might teach you. Brenna, Astrid and Brynhild also speak Old Norse. It is closely related to it. Unless it is the All-Tongue you would like to learn. I do not know if it is possible for humans to do so. It consists of more than just words.