Permissions based on User ID

good day.

In my new company, we have 2 partners. One resides in country X and other in Y, both of them are system users with administrative ranks in the ERPnext. ERPnext has only been implement in Country Y. Further, purchases will only be made from Country X

Now for the pruchase order, we want to make it in such a way that if partner in Country X creates the purchase order, we will approve it here and if we create a purchase order, partner in Country X will approve it.

how is it possible?

You can do that using custom script in Purchase Order