I followed the tutorial on ’https://www.digitalocean.com/community/tutorials/how-to-configure-nginx-to-use-custom-error-pages-on-ubuntu-14-04’ to add a custom 404 page to my ip but instead of showing 404 page it shows internal sever error
my error log is :

2019/10/31 13:42:18 [emerg] 12796#12796: duplicate location “/testing” in /etc/nginx/sites-enabled/default:94
2019/10/31 13:42:43 [emerg] 12828#12828: duplicate location “/testing” in /etc/nginx/sites-enabled/default:94
2019/10/31 13:46:06 [emerg] 12871#12871: unknown directive “First” in /etc/nginx/sites-enabled/default:51
2019/10/31 13:48:22 [emerg] 12905#12905: unknown directive “First” in /etc/nginx/sites-enabled/default:51
2019/10/31 13:51:43 [emerg] 12941#12941: unknown directive “First” in /etc/nginx/sites-enabled/default:51
2019/10/31 13:54:48 [emerg] 12979#12979: unknown directive “First” in /etc/nginx/sites-enabled/default:51
2019/10/31 14:02:05 [emerg] 13058#13058: duplicate location “/testing” in /etc/nginx/sites-enabled/default:95
2019/10/31 14:02:23 [emerg] 13090#13090: duplicate location “/testing” in /etc/nginx/sites-enabled/default:95
2019/10/31 15:24:34 [emerg] 13848#13848: duplicate location “/custom_404.html” in /etc/nginx/sites-enabled/default:80