How Manu dedicated server slots i could provide with my 512/512 ??

it's completely up to you. i personally would set it to 16. it may create a little too much lag, but you can always lower it if too many people are complaining.

ok, i think i maybe make like 14 (different game's)
but i only keep server sometimes i sleep, or i keep it and play it with other pc upstairs...

join sometimes if u see it name is often some kind like: wilsoldat.cjb.net