JP: Translated avatar heading, website heading, and changed medium to above average

Please let me know if my Japanese is incorrect.

Translated the avatar heading to アヴァター
Translated the website heading to ウェブサイト
Also, I noticed there is no equivalent of "Medium difficulty" in Japanese, so I changed it to "Above Average" (平均以上)
If "Above Average" is too much, would "Average" (平均) be better?