@Shota Akhalaia, You can re-install/recover the ambari for a existing cluster only if you have the backup of ambari database. Otherwise there is no easy way to point existing cluster to existing HDP cluster. The only option is to install a fresh ambari along with fresh HDP.
If there was no Ambari Server installed already or if the Ambari DB is lost (corrupted / no backups) then Ambari Takeover is a process which can be used. But it completely depends on which kind of components you have installed and it is usually a tough process to setup Ambari over an existing HDP cluster.