Login/Redirect issues

Greetings! After days and nights of digging into WP, code, plugins, etc..and a beginner at that, i’m almost there.
I’m using Multisite. I have 4 sites and users to match. Here’s the issue.

I will be sending clients the same login link to their page each time
they have new files available for download.
url/page/wp-login.php? which takes them to url/page

Once user1 has logged into their site, (url/page) IF they click on that same link OR a link to any other page i’ve created, it takes them to the wp-admin/profile.php of the original user (user1). While logged in, if they click on the link to would like to take them to the url/page OR to log them out if they click on the link.

Follow?
Please help.
Thank you!