A lot of users speak a language other than English and we depend on contributions to make Proxmox VE available to users all over the world. We are always happy to welcome new localizers and invite you to help shape Proxmox VE.
Our language files are available as git repository. If you are familiar with git we would be glad to see your contribution according to our Developer Documentation.
Nonetheless, translating does not require special technical skills. You can get the language files without setting up a development environment here. Right click on the "raw" link of your language and choose "Save Link As…". Do not hesitate to send your translation directly to office(at)proxmox.com with your signed contributor license agreement.