htaccess rules - multi-language website - .htaccess

Question

I created a language script in my website. This script recognizes the language in the URL and loads the language definitions.
For example:
RewriteRule ^(.+)/about/?$ sobre2.php?lang=$1 <-- working fine
RewriteRule ^(.+)/contact/?$ contato2.php?lang=$1 <-- working fine
RewriteRule ^(.+)/products/?$ produtos2.php?lang=$1 <-- working fine
RewriteRule ^(.+)/contact/sales/?$ contato-vendas2.php?lang=$1 <-- working fine
RewriteRule ^(.+)/contact/general/?$ contato-form2.php?lang=$1 <-- working fine
The pages above are accessed, respectively, as this:
https://domain.com/b2b/pt-br/about/
https://domain.com/b2b/pt-br/contact/
https://domain.com/b2b/pt-br/products/
https://domain.com/b2b/pt-br/contact/sales/
https://domain.com/b2b/pt-br/contact/general/
This is working fine in all pages, except index.
When I try to do the same thing with the index page, using this code:
RewriteRule ^(.+)/?$ index2.php?lang=$1
Besides it doesn't work, it also affects all the other pages (and resources), so the resources are not loaded and the page looks like a "pure html".
I'd like to know how can I configure the htaccess to make my "index2.php" be accessible like this:
https://domain.com/b2b/pt-br/
Thank you.

Answer 1

.+ will match 1 or more of any character and if you place rule before other rules then this will make other rules ineffective.
You can use these rules:
RewriteEngine On
RewriteBase /b2b/
RewriteRule ^((?!pt-br/).*)$ pt-br/$1 [L,R=301,NC]
RewriteRule ^(.+)/about/?$ sobre2.php?lang=$1 [L,QSA]
RewriteRule ^(.+)/contact/?$ contato2.php?lang=$1 [L,QSA]
RewriteRule ^(.+)/products/?$ produtos2.php?lang=$1 [L,QSA]
RewriteRule ^(.+)/contact/sales/?$ contato-vendas2.php?lang=$1 [L,QSA]
RewriteRule ^(.+)/contact/general/?$ contato-form2.php?lang=$1 [L,QSA]
RewriteRule ^([a-z]{2}-[a-z]{2})/?$ index2.php?lang=$1 [NC,L,QSA]