What is the ruling on my excessive whispering (waswasah) in intention and extravagance in ablution (wudu), and is the method my mother taught me for Istinja' (cleansing after defecation or urination) with water sufficient, by washing the front private part with the hand, knowing that I exaggerate in Istinja' and insert my finger into the inner part of the vagina due to my doubt about water reaching every part, which causes me pain? And is it obligatory to wash the front private part section by section, or is it permissible to wash all parts together?

You must continue to resist and ignore obsessive thoughts until you are cured of them. As for the intention, it is sufficient to bring the prayer to mind inwardly, and then commence it. To remedy excessive water usage, do not wash a limb more than three times. Regarding istinja (definition)’ (cleaning oneself after relieving oneself), the method your mother taught you is correct. It is sufficient to have a strong presumption that the area is clean by pouring water over the entire defiled spot; certainty is not required. Ignore any obsessive thoughts after that.