Firstly, "得"should be attached to a verb . It's a pattern as "verb. + 得 + adj."
e.g. 跑得快,叫得响
So if you want to follow your "subject+ verb" pattern to correct the sentence it should be "他说汉语说得真好"
However it would be more concise to delete the first verb ."说" , as "他汉语说得真好"。