Configure 2 trunk ports on MKT RB750

Hi Mikrotik Forum.
Please help on solving a problem related to configuring 2 ports as trunks.
I attached a scheme on what we intend to do. so far we managed to configure the incoming connection to port 1(trunk), and acces ports(2, 3, 4). Now the problem is how to configure the fifth ports as trunk and pass tagged frames from port 1 to the 5’th.

Thank in advance
Drawing1.png