It is silly fo you not to forgive others for their mistakes.可以说成
问题描述：
It is silly fo you not to forgive others for their mistakes.可以说成
It is silly fo you to don't forgive others for their mistakes.
不是说It is+adj.of sb.(not)to do sth.
答
只能用It is+adj.of sb.(not)to do sth.这个句式
不定式 to加动词原形哦 不可能是 to don't
所以表示否定只能说 to not forgive 明白?