Crazy error with Management Interface

[Derek1993]

Hello evryone! Need Help!

I have already configured my FP 1120 via Firepower Device Manager - all is Ok. But after some times I receive error: On mai window of ftd my ISP icon is grey and NTP Service doesn't work - also grey! I know that there is an error with Management Interface, BUT I cann't uderstandt what configuration is correct. So for now my Management Interface Configuration is: 
Use Unique Gateways for the Management Interface with Fallback to Data Interfaces

output of command show network:

DNS Servers               : 1.1.1.1
                            1.0.0.1
DNS from router           : disabled
Management port           : 8305
IPv4 Default route
  Gateway                 : data-interfaces

==================[ management0 ]===================
Admin State               : enabled
Admin Speed               : 1gbps
Operation Speed           : indeterminate
Link                      : link-down
Channels                  : Management & Events
Mode                      : Non-Autonegotiation
MDI/MDIX                  : Auto/MDIX
MTU                       : 1500
MAC Address               : 40:06:D5:85:FF:80
----------------------[ IPv4 ]----------------------
Configuration             : DHCP
----------------------[ IPv6 ]----------------------
Configuration             : Disabled

===============[ Proxy Information ]================
State                     : Disabled
Authentication            : Disabled

I have tried also using static route for my FP 1120 - Did work!
Plz Help ! 

[Derek1993]

Thx for answer in my situation, what configuration I must to use for Management interface ?
Because I have Internet on clients via FP 1120, but Management inerface is not work correctly, and I cann't receive any updates and configure NTP server for my FP 1120 ??

[Derek1993]

@MHM Cisco World I want to configure FP 1120 Management interface without any connection Cabel to Management Interface ??

[MHM Cisco World]

without cable connect you can not config mgmt dedicate interface 

You need to config data interface as mgmt interface, this no need any cable 
you can convert data interface to use as mgmt interface with option managment-only in advance tab 

[Derek1993]

and One More Thing, I have like this error:
Gateway cannot be reached through port Ethernet1/1 named “outside"
Any ideas: @MHM Cisco World @Aref Alsouqi @Kasun Bandara 
BUT I all my clients receive Internet via DHCp from FP 1120 ??? 

[Derek1993]

@All Plz Help I need your support ! I still have issue and My Management interface doesn't work correct !