I am developing a e commerce website using Django I was done with front end now I need to do back end $.$

I need to make register and long management how can I achive that

When we open the site the register page should need open if the user is new to the site he need to register the site after register he can login with the credentials and he can login into site

Note a proper validation should be done for the both registration page and login page

And another one there is contact page where the user will fill. The details and that details should come to the admin through mail and data should be stored in Data base

Guide me step by step so that I can archive the gal and complete my project