"Hello! I'd like to ask if it's possible to install two MS scripts on one website?"
Yes and no. It's technically possible, but we don't recommend it.
Things will start to break if you have the header script installed twice on the same page. Which means you can only install two scripts if create two entirely distinct membership areas on your site.
You would need two signup & login pages (each with different scripts in the header) and members will need separate accounts to login to each area.