Apache mod-proxy modify header as Forward Proxy

Question

i'm using apache server as proxy in order to add some custom headers to the request forwarded to a website on the internet. I want apache like a man in the middle. The browser send a request, apache receives it, it add some headers and then apache forward the request to the original request endpoint.

Instead of:

browser ---> website

I want:

browser --> apache add headers --> website

How can i achieve my goal in the simplest way?

I tried as forward proxy but the header is not added

<VirtualHost *:*>
   ProxyRequests On
   ProxyVia On
   <Proxy *>
       Require all granted
   </Proxy>
   Header set header "headerValue"
   RequestHeader set header2 "header2value"
</VirtualHost> 

then i tried as reverse proxy but the website couldn't load some static resource 'cause the Host header was overrided with the proxy Host.

<VirtualHost _default_:82>
    ProxyPreserveHost  Off
    ProxyRequests Off
    ProxyVia On
    ProxyTimeout 300
        <Proxy *>
        Allow from all
        </Proxy>
        ProxyPass /something/something/ http://externalwebsite.com/something/something/
        ProxyPassReverse /something/something/ http://externalwebsite.com/something/something/
        
</VirtualHost>

RequestHeader set header2 "header2value"

Can you help me pls?

Thank you very much