I love the spirit of this build!
And your English is great. Don't worry about it. And I love that you're just digging in and not being too precious about everything.
The one design comment is the high lever-arm you have on that tall z. If you don't need to be cutting tall things, you might consider tightening that up.
Oh and 4 foot ballscrews are long enough where they can "whip" if you spin them too fast so you may have to keep the travel speeds down a bit to avoid that, especially since your screws won't be super high precision. But it's just something to plan for... Not a real problem if you know about it.
excited to see this progress!
-jesse