What must I do to rectify the two Umrahs I performed, knowing that I shortened a little of my hair in them based on a fatwa I heard, and now I have learned that complete shortening was required?

The pilgrim (performing Umrah) must shave his head or shorten his hair, and shaving is preferable. It is obligatory for him to shave his entire head, according to the preponderant opinion, which is the madhhab of Malik and Ahmad. Their proof is that the Prophet (peace be be upon him) shaved his entire head. Abu Hanifa held the opinion that it is sufficient to shorten a quarter of the head, and Al-Shafi'i held that the minimum sufficient is three hairs, whether by shaving or shortening. There is no disagreement among them regarding the preference of shaving the entire head over shortening, due to Allah's saying: (having shaven your heads and shortened). As for someone who only took from some of his hair, relying on the opinion of those who say so, there is no blame on him, and nothing is currently obligatory upon him, because the matter is one of ijtihad (independent reasoning). However, in his next Umrah or Hajj, the shortening or shaving must encompass the entire head.