True, and funnily enough french people don’t use yearly gross. Most of the time they use monthly net, and, in the context of salary negotiations, will specify over how many months. E.g. “2000 net sur 13 mois”

Imho, the java aspect of it matters much less than the backend concepts. Are you already familiar with those ?

There’s quite a lot of stuff to learn on the backend and it really depends on which layer you want to focus on. If you’re interested in developing business services then i would recommend writing a restful API (for example for a to-do app) with spring boot and your preferred flavor of SQL database. That covers a lot already. From there you can look at how to scale performance up (caching, queuing, asynchronous).