How do pharma drugs actually end up on pharmacy shelves? And why the difference between countries?

I live in Europe and I’m struggling to get drugs that a family member needs in my country. When I say struggling I mean I can’t.

At the same time I see them on sale in eg Germany and France.

I’d like to understand more about why they’re not available in my country – but are in others. I’m not a medical professional or student so if this question seems dumb just direct me to the right links and I’ll read up. I honestly had no idea what to start googling.

If anyone else faced a problem like this – how did you solve it? Drugs don’t seem to be “orderable” online from across border in Europe, unless I’m mistaken?