what ist the requirement for replication? another hyper-v server?
Yep, target hyper-v server is required in case of replication.
what is the requirement for backup? nas ? hyper-v server?
The role of backup repository (the place where corresponding backup data is stored) can be played by
• Windows server with a local or directly attached storage (local disk, USB hard drive, or iSCSI/FC SAN LUN)
• Linux server with local, directly attached storage or mounted NFS (local disk, USB hard drive, NFS share, or iSCSI/FC SAN LUN).
• CIFS (SMB) share. However, please be aware that Veeam agents are not supported on SMB share, thus, data to the SMB should be written with a usage of Windows-based proxying server that might be either default VB&R server or any other Windows based machine.
what is the requirement for wan acceleration?
Similar to proxy role, the role of WAN Accelerator can be assigned to any Windows based machine in your environment. Also, WAN Accelerators should be specified at both ends – source, as well as, target location.
is there anywhere some short description which hardware is necessary?
I believe, there is none. However, you might want to take a look at corresponding User Guide, since all the questions you have are pretty good covered there.