Try putting some rewrite rules like this in your .htaccess
file:
RewriteEngine on
RewriteBase /
# Make sure it's not an actual file or
# directory, being accessed. If you wish.
#RewriteCond %{REQUEST_FILENAME} !-f
#RewriteCond %{REQUEST_FILENAME} !-d
# Match the subdomain
RewriteCond %{HTTP_HOST} !^www\.example\.com$
RewriteCond %{HTTP_HOST} ^(.*)\.example\.com$
# Rewrite the request to the main domain:
# %1: The subdomain matched against HTTP_HOST in the previous RewriteCond.
# $1: The request URI.
RewriteRule ^(.*)$ https://example.com/fixed/%1/$1 [L,R,QSA]
Feel free to drop the L
flag, if it’s not the last rewrite rule. See RewriteRule Flags for more information on this.
You can test it online.