Walaikumussalam
Standing in shower is not correct method of ghusl
Because your ghusl is tarteebi which suppose to be perform in order .
First remove the Najasat then do the niyat of the ghusl and first wash your head and neck then right part from shoulder to foot then wash left from shoulder to foot . This is the ruling you may see in tauzeehul Masayel also
Wassalam