Cannot login

Hello,
I installed the plugin, but I did not set any custom url.
I thought the usual wp-admin url would work.
Instead I can’t login if I try to use the regular website.com/wp-admin. When I try, I’m shown the typical page I can see for other websites where I’ve installed the same plugin and I try to go to the regular wp-admin login page, a messed up page.

It seems that a custom url for wp-admin has been set, without me setting it up.
And I dont’ know this url, so I’m locked out.

How could you help me? What should I do to log in?
Thanks a lot for your kind help.
Mario

https://wordpress.org/plugins/wps-hide-login/