I have trouble following the advanced level class.
Koichiko seems to have been bullied by high level students.
Some non-native speakers speak English at a native or advanced level, while others do not.
When you are at an above rank, you are at an advanced level. This is referring to things like proficiency in Japanese, or things like that.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.