.htaccess issues

Hi Friends,
i’ve setup wp job manager in a new wordpress installation. This new installattion is inside a subfolder from a previous wordpress installation.
I had:
http://www.oldwebsite.com.br
Where i have a .htaccess file up and running correctly.

Now i have:
http://www.oldwebsite.com.br/new-website-with-wpjm/
Where i had to remove .htaccess because it was redirecting to old site or having a blank page as error 404.
Now it’s working fine however with ugly urls and so i can’t optimize to seo purposes.

My question is what should be .htaccess directives in order to avoid wrong redirection to my old site. Url from new site must redirect to pages inside new subfolder.

I appreciate some direction. Thanks.

https://wordpress.org/plugins/wp-job-manager/