Loic_B:
No one is wasting his time here. As long as we have fun.
You can adapt a 36 hp VW motor to a 1-ton pickup. It'll probably be able to push it down the street, but not up much of a hill, if any. The 100-hours of work may have been educational and fun, but ends with, 'The result was nothing vaguely useful, so why did I bother trying?'
Pick a 'scavenger' project that has at least -potential- for being something more than 'not vaguely useful at all,' and you'll get enthusiastic support. I won't waste -my- time supporting anything that has no (read: zero) purpose, not even for the fun, because it's not fun when it 'does nothing.'
...to understand what kind of input this LCD screen need. Do you have a hint ?
Sure. You know the graphics chip number. Go find the docs and it'll tell you exactly what -it- outputs. All you need to do is emulate that with Arduino.
Or, leave the graphics chip circuitry intact, and with Arduino tell the chip what to do on the screen.