@CristianoP A great resource is to download the manual for the switches from the support page.  There are several examples of setting up 802.1q VLANs in there.

For yours, assuming VLAN 1 is the native network for the SG108E, set all ports to have a PVID of 1, and VLAN 1 as untagged.  For port 1 & 4, set VLANs 2, 3, 4 as tagged.  That will trunk those two ports to carry the VLANs through to the SG105E.

Assuming the SG105E is also natively on VLAN 1, set port 1 like port 1 of the SG108E.  Then each of the other ports will have a PVID and untagged VLAN for there respective connections, and no tagged VLANs on those ports.

That should work as you have shown in the diagram.

I just notice the two LAGged ports, you should be able to set those up before or after the VLAN settings.

And this assumes Pfsense is setup to trunk the VLANs out to the first switch.

@JoeSea and @Somnus 

Many thanks for the information/instructions.
I did according to the screens below and it worked perfectly.

  @CristianoP Oh carful, on the SG105E only ports 1 & 3 should be untagged on VLAN 1.  You really don't want two untagged VLANs on the same port, since the VLAN setting is ambiguous if the client does not have an established IP.

  @JoeSea 

Hi JoeSea.
I adjusted according to the attached image; thanks for the alert.