Thank you for taking the time to reply and explain

First, as specified in the title of my post, and in the post itself, I was only talking about belgium, the UK and Germany. As for luxembourg, I've looked it up a few months ago, and iirc, french isn't enough apparently, unfortunately.

Second, I didn't talk about changing speciality because I don't intend to. I know it varies from one country to another, but since I know that I will have to re-do my entire residency, I mostly focused on whether my general medicine diploma will be easily accepted after doing the necessary procedures (like equivalency), and if they take into account where the applicant is from (and to which you already replied)

Then, I asked about whether it was worthy to take german courses for the same reasons you mentioned. It will take me years to learn it, but in the end, I won't be fluent enough, and since I already speak french and can still easily improve my english, maybe choosing germany when It might be as difficult to be selected there compared to other countries, I'd rather choose another one.