certainly当然地,肯定地（语义稍轻）；absolutely绝对地,完全地（语义较重）；
这句话应该certainly较好
下面这句话,应该是：
I have been keeping making mistake about English every minutes.（keep后接V-ing)
或者直接说：
I have been making mistake about English every minutes.(keep doing sth和现在完成进行时态意思差不多,同时用有点重复的感觉）