Cannot access wp-admin for a duplicate site under folder

I just made a duplicate (duplsite) of my main wp site under a folder of the main domain, e.g. “domain.com/duplsite“. I made a new database for the duplsite and imported the data from the main db (they are now identical). I also copied the content of “wp-content” folder from main site to duplsite.

When I now look up the duplsite, domain.com/duplsite, it turns up normally except no posts are visible (empty blog). When hovering over the menu all links are still directed to the main site, so this I need to change.

When I try to access the admin part of duplsite I get automatically redirected to “mainsite/wp-admin”, so WP is redirecting me to the main site.

Can I find a workaround to access duplsite admin part?