Hi! First, you'll want to find a RegEx pattern that matches /val_1/val_2 (with an optional trailing backslash): ^/(.*?)/(.*?)/?$, then you'll want to map val1 and val2 to a query string:

rewrite ^/(.*?)/(.*?)/?$ /?var_1=$1&var_2=$2&$args

&$args appends the rest of the original query string to the request, so that for example http://domain.com/val_1/val_2/?something=abcd works as expected.

Make sure you restart nginx after editing the config file.