There is several ways of hosting a file server, it depends completely on what you have available to you and the limits
1. if your hosting a csgo/css/cs1.6 server off your pc or paying for a GSP [Game Server Provider] You will 100% need to go with a web hosting service, they can be had for cheap
2. if your hosting your cs server on a dedicated rack running Windows you have a few options
1. Xampp [
https://www.apachefriends.org/index.html] comes with an Apache HTML/PHP File Server and im sure it can be run under Wine in linux
2. I personally prefer HFS "Http File Server" [
https://www.rejetto.com/hfs/] my clan uses it not for our FastDL, but for a few other things, such as backups / minecraft world backups / other stuff
Xampp Is tricky and im not the one to explain it but HFS is simple, you run the EXE, Turn it on, and add your cs directory as a virtual folder
it will then give you an ip... this is mine ***REMOVED IP*** if youd like to demo it
and the you navigate to the cs directory and it should give you an adress
000.00.00.000/csdirectory
and you ad that to Sv_downloadurl