I Can Turn into a Fish - Chapter 41 - Plateau and sales volume

When Li Xianyu was 20 years old, he received his father’s inheritance, an 18-year-old great-grandmother who was incredibly beautiful.

Li Xianyu: “Great-Grandma, why are you so young?”

Great-Grandma: “That’s because I died when I was 18 years old.”

- Description from Novelupdates

He became a teacher at the best magic academy in the empire.
….For being mistaken for someone else.

The third young master of the Gu household, Gu Ye, had a wooden personality, a stuttering speech, couldn’t remember an answer after being told ten times, didn’t dare to protest after being bullied, was considered the shame of high society. His father, in a fit of anger, sent him back to the old home in the country for the new year. But unexpectedly, he came back like a new person, in half a year testing into the top university of the capital with the highest score in the whole school.

Because I like to collect antiques, I was accidentally brought to a magical world by a crystal skull in my collection.

- Description from novelbuddy