salut le belge,
The longest trip I have done is about 2-3 months, so what I can add is that being away for a very long time is perhaps something that you will not like, or maybe get tired of.
My suggestion is to get a good, basic bike with easily replaced parts and good well built panniers and racks, and then see how your first "section" goes and then plan more for the next section.
When I started getting into touring somewhere around your age, I didn't know much about fixing bikes, but I did start making the effort to start learning and getting my hands dirty doing things---on any long bike trip, being more comfortable fixing the basic things and learning to recognize things before they become a problem is a big advantage.
I've met some riders doing really long trips who had very little mechanical knowledge, but it is in your best interests to become more knowledgeable.

good luck with your dream.
I would have loved to have done this when younger if I had had a suitable partner to do it with. I personally wouldn't have wanted to do it alone.