External FTP access

Good Morning,

I have a MK RB750UP and I’m having problems with my internal clients to access external FTP servers.

I have a proxy on Debian that does all the content filter and is connected to the MK.

My clients are in a network (192.168.0.0/24) and the proxy is on another network (172.16.0.0/30), Mikrotik has 3 interfaces.

Interface 1: Internet - Public IP
Interface 2: 192.168.0.1/24
Interface 3: 172.16.0.1/30

I made a rule of the ports 20 and 21 and also forward a rule to established and related connections, but this rule does not work.

Does anyone have any tips to help?

Thank you so much!
Oliver Guerino