应该都是可以的
用of的话在句子里就翻译成 享受学英语的原因;
用for的话就翻译成 为了享受学英语的原因。
应该填of 翻译为 享受学英语的原因
没有填for的用法
“。。。。。。的原因”这样表达“the reason for...,the cause of... ”
These are my reasons _for____ enjoying learning English.
These are my reasons why I enjoy learning English.
These are my reasons (which/that) I enjoy learning English for.
of 固定搭配 the reason of