Menu modal (popup) login on main site

For my multisite i want to have a modul login popup in the menubar. So in the menu there is a tab named "Log in", and when it's clicked a login modal/pop up will show. Like on the pictures.
Altso, when someone login on the mainsite i want them to get redirected to their own wp-admin. If they login from the wp-admin on the main site, they can't access their own, before they go to their site.