You may think Ronaldo scored more goals in this season because he is now more experienced in the Saudi league and he knows the league better than before but the fact about Ronaldo is he is also getting older and he shouldn't have better performance normally because of his age.
Ronaldo is a 38-year-old player and usually, a player gets retires before this age while he scored 20 goals and had 9 assists in 18 games so far.
At least that hasn't been seen with Ronaldo currently, maybe because he has very good support at Al Nassr so he can get good passes so it's quite easy for him to execute them into goals. But that won't last forever because one day he will retire, maybe at the age of 40 but when he retires it won't be because the quality of his game has decreased sharply but because it is time to retire because at the age of 40 it will be increasingly difficult for him to keep playing for 90 minutes, and retiring while still in a good position would be a better note for his career than retiring when there are many problems with his body.