Your explanation is a bit confusing
yes, i have the paper wallet private-key. thats the one i have to use? i used that paperwallet private key to create the watch only wallet. but if i use the same private key in the watch only wallet, nothing happens. because bitcoins are not anymore in the paperwallet, they are in the watch-only wallet.
Importing with a private key would not result in a watch only address, this only happens when you use the master public key. If you used keys from the paper wallet, you should be able to recover the funds if you have the xpriv as all child addresses are linked in a HD wallet.
If you swept the funds then, it was sent to a completely new address from the paper wallet and as such keys from it will not work.