Ammo and unit types

I'm pretty new to the rules. I understand that ammo for vehicle AP & HE is limited and tracked, but should I also track ammo for infantry AT weapons like a bazooka or a panzerschreck? If so how much ammo do they have? Same question for guns both AT and otherwise.

Also, when tracking ammo and using an "Open Fire!" order. If the vehicle spots and fires twice, I assume that this uses two ammo and not just one. Is that correct?

Infantry  AT weapons have unlimited ammo. Exception, obviously is the single shot panzerfausts.
All types of deployed guns also have unlimited ammo.
If you spot twice, you fired twice. So, mark down 2 ammo as used.

Hope that helps,

Best regards,

Diego

Even the deathbringing Panzerschreck? I thought, my unit has only one shot.

Thanks!