Must I make up the prayers whose validity I doubt, in which I did not wash the navel during ghusl from janabah? Is it necessary to forgo recreation to speed up making them up? And is my question considered seeking out dispensations?

Doubt concerning an act of worship after its completion does not invalidate it. So, if the doubt is merely a whisper (waswas) about the validity of the prayer or the speed of recitation, it should be disregarded. However, if you become certain that you performed some prayers without fulfilling all of their pillars (arkaan), you must repeat them immediately according to the majority of scholars, as long as it does not harm your body or livelihood, in accordance with the verse: "So fear Allah as much as you are able" (Quran 64:16). As for doubting the washing of the navel during ghusl al-janabah (ritual bath after major impurity), the strong presumption that the entire body has been covered with water is sufficient, and rubbing (dalk) is not obligatory according to the majority of scholars. Furthermore, making oneself hear one's recitation in prayer is not obligatory according to some scholars, and it is permissible to adopt this view when it is difficult to make up (for past prayers). Your asking about matters of your religion is not seeking concessions (rukhs), but rather it is precisely the right thing to do. We recommend turning away from waswas (whispers of the devil) and not giving in to them.