Duplicator plug in - login and theme not available


I had installed Duplicator in order to create a copy to my WP web-site and to install it on my hosting (adding mywebsite/testing) where to make experiments without affecting the current web-site. I had managed to save the current website, I created a new directory on my host space (.../testing) where I installed the web-site and from here I see that my theme is not working anymore (mainly the CSS i think) and neither the log in (when Im trying to log-in it shows me "The page isn`t redirecting properly/This problem can sometimes be caused by disabling or refusing to accept cookies." and I had checked the Mozilla settings and where ok, and after I tried with Chrome and it said "The web page has a redirect loop"). I had made an detailed search through Duplicator help but couldn’t find a solution.
Can you please help me?

Thank you very much!