Transfer Main WordPress Website to Subdomain

Hi! Good day! I would like to ask some help and advise on how to correctly transfer my main WordPress website to a subdomain.

Scenario:

I want to transfer my website to a new subdomain, ex:
from web.domain to old.web.domain

I want to make a new design of web.domain without losing the original site, just transfer it to old.web.domain.

I know its possible I just don’t know how. Please help!

I TRIED:
#1 Downloading all files in web.domain in my hosting through FTP and uploaded it to old.web.domain plus i edit a Db which is wp_options; siteurl and home fields and input old.web.domain. No luck!

#2 Added

define('WP_HOME','https://old.web.domain'); 
define('WP_SITEURL','https://old.web.domain');

in wp-config.php before ‘That’s all, stop editing! Happy blogging’

I’m not a coder, I just Google things and run out of options, can’t find solutions. I hope you can help me and sorry for my English.

[ Signature deleted ]