Not sure would say "the poor countries" - generalizations in English drop the definite article.
I reported "... are arriving ..." was not accepted.
Correction: "the poor countries" is not acceptable in this particular sentence. Please, review.
Many people, or a lot of people is not the same?
That's not proper English ! ... "arriving from THE poor countries" !
Yes it is; if you are talking about some poor countries in a group.