I create a resource group with 2 server sql i selected thr whole instance. So i chech i can restore once database from instance. But when i want to create manually backup of one database i cannot do it there is only backup of whole resource group so i have backup of both servers. Its this not possible because i use resourcefgroups? Or how can i do manually backup of one database?
When you create a resource group, backup is taken at the resource group level. Backup happens for the resources grouped, irrespective of whether you had selected the whole SQL instance or selected multiple individual DBs while creating the resource group.
If your intention is to backup a single SQL DB, then you will need to protect the SQL DB individually.