

By the way, is there a rule to how these short forms are formed?
Yep! Most Japanese verbs (with a few exceptions like ‘shimasu’ becoming suru) use one of the ‘i’ variants (‘i’, ‘ki’, ‘ni’, ‘mi’, or ‘ri’) after the kanji, that indicates they are verbs.
Yakimasu (to burn/ cook), shirimasu (to know), arukimasu (to walk), arimasu (to be), shinimasu (to die), yogimasu (to read).
Ki will become ku in the shortened version, ri will become ru, ni -> nu, etc:
yaku, shiru, aruku, aru, shinu, yomu
I believe the verbs that don’t end in one of those like tabemasu (to eat) will default to ‘ru’ (taberu), but I don’t know if that’s a rule off the top of my head, or if I just can’t think of any others right now.
In the cases where rendaku applies, such as yogimasu (to swim), the end kana will also have rendaku applied, e.g. yogu. Ki -> ku, gi -> gu.
Nope, just been learning and speaking it for a long time. :)
Good luck with your studies, and you can always dm me if you have any other questions!