Can change the number of ammo of M4A1 30/90 to 50/1000?

I don't know why you want that much ammo. But no.

CS2D doen't have that feature. You will have to do it completely in Lua: count shots manually, fast reload if there still 20/50 bullets inside. Also you have to show the ammo information to the player (hudtxt2 is the simpliest way)

This would be useless anyway...
use the INF ammo instead .

No, Use inf ammo

No you better Use INF-ammo

There's no point in posting the exactly same thing multiple times. It's spam and not allowed. So please don't do it. Thanks.
btw: The command/setting is called mp_infammo

Exactly.

Additional info:
KabirDuy, p90 have 50 shells in magazine.
So write in console this:

1.) Infinity ammo.
2.) Set damage of p90 as m4a1.
And use p90 instead m4a1.