I mentioned in the beginning the diphtongs in Old Gutnish which are ai, au, and oy. Well, the same goes for Modern Gutnish. It hasn´t changed. But we have some more diphtongs nowadays. In Old Gutnish we have the long vowels e, i, o, u, and y which in some words changed into a diphtong. The same trend has been seen in a few more scandinavian dialects or languages. Maybe the closest language to Gutnish in this regard is Faroese. In Gutnish this process could have started maybe in the 15th or 16th century, or probably not later than the 17th century.
In our language and in these cases e turned into an ei-sound (as in a in English later) and spelled é, the i has about the same sound, just a smaller difference and is written í or ei. The Old Gutnish o is about the same sound as in English bow and is no written as ó. The u is now written as ú or eu and pronounced like an eu-dipthong, and y has become ý.
koyre (to drive)
lére (to learn)