Getting started ,looking to become a DPO

Hello ,
I am a second mate from Greece with experience in bulk carriers,crude oil tankers and container carriers and I would like to know everything about DPOs because is something Like I was looking for a long time. I know about the courses at the nautical institute as well as the different costs at each country, but can i work as a junior dpo in a foreign company or there is any problem concerning my nationality? I also must know about the (monthly) salary and if there is any company that can sponsor my studies as a dpo because there is no such thing here in Greece. Is it really that the contracts are 1 month on/off? Because my contracts until now were 6-7 months on .
Thanks in advance for any information provided .