Q: I don’t know if all the hairs on my back got wet in ghusl and also I soaped the flat bit under the private parts and the arm pits. Would the rest of the hairs on the body get wet on there own under the shower? I see hair standing up, would they be washed?
A: Don’t pay attention to these stray thoughts. If you follow the normal procedure, insha-Allah your ghusl will valid.
And Allah Ta’ala (الله تعالى) knows best.