这句话的错误主要是后半句indeed的用法不准确。正确句子应该改为,but I ran very fast indeed.

    按照英语惯用，indeed置于形容词或副词后，在一般与very连用。例如：This is a very good answer indeed. Thank you very much indeed.

Indeed 可以单独用于句首或句子中间的形容词前，这时不需要和very连用，例如：Indeed, I am grateful to you. Ｉam indeed grateful to you.