I have a domain in “hostalia” which points to “000webhost”. When changing the dns to point to cloudflare, will there be a connection between the domain (hostalia) and the hosting (000webhost), or will I lose it?
As you have stated you have a domain which is pointed to 000webhost.
To use Cloudflare, you would need to add your domain to your Cloudflare account and in the process of adding it, you will get new nameservers provided by the Cloudflare.
Moreover, that nameservers you would get from the Cloudflare in that process, you would need to add them or change the current ones to the new Cloudflare’s at your domain registar under “Custom Nameservers” to make it work.
Upon correctly added/changed nameservers, your domain will point to Cloudflare and resolve successfully.
There will be some next steps to configure in case if needed, like the SSL connection. cache, optimizations, security, etc.
In case of any issues, you can always write back with some feedback information about your issues or errors.
As @DotMrCode pointed usefull links, please find more information here: