Can't find Windows Server 2016 to download

AdisCatrnja If your still looking for this, I could download the ISO from here:

https://www.microsoft.com/en-us/evalcenter/evaluate-windows-server-2016

You can use these instructions to convert the trial version to a retail version with your product key:

https://docs.microsoft.com/en-gb/windows-server/get-started/supported-upgrade-paths

Make sure to check out the dedicated community for Windows Server, which is the best place to ask questions about this topic

https://techcommunity.microsoft.com/t5/Windows-Server/ct-p/Windows-Server 

Hope that helps.