I just have a couple of questions regarding ghusl janabah and prayers.

1. If someone went for a shower with the intention of performing ghusl janabah but they did not do the full niyat (ghusl janabah wajib qurbatan il-allah allahu akbar) would their ghusl be valid? Would their prayers after also be valid?

2. If someone, after washing, with soap and shampoo, their head and body in the shower, intends to do ghusl janabah would they still have to wash their full body with water or just niyat and leave the shower since they have already washed their whole body and water has gone everywhere?

1- They don’t have to say the niya, they can make the niya in their heart. They need to know what they are doing and who they are doing it for. That is sufficient.

2- They have to perform the full ghusl correctly after the niya. The washing before the niya does not count towards the ghusl.