Nginx redirect won't let me into Joomla admin?

Question

Nginx

There is a VDS with a simple site on Joomla 3. I decided to part with Apache and finally move to Nginx + php-fpm. I like everything very much, and subjectively faster, and pagespeed agrees with me.
The problem is the following. I made redirects, I remove the slash with this construction:

if (!-f $request_filename) {
     rewrite ^/(.*)/$ /$1 permanent;
   }

after which the login to the admin panel stops working. Writes ERR_TOO_MANY_REDIRECTS or, in other words, the site has redirected too many times. The rest of the site continues to work.

Maybe someone will tell you how to remove the slash and get into the admin panel? Thanks to all who answered.