Am I going to get fired?

It probably means that they are going to get you a motorized pusher to help you out. Or a helper. It could mean that with only 2 weeks on the job you may have to take the lead role and eventually be supervisor of the parking lot. So, always remember to be nice and not let things get you down.

If you are working as hard as you can and not goofing off and doing as little as you can you won't be fired. But if they see you taking it real slow and hating it, you may be. If you can't do the job alone, tell your boss you need help.

I don't know.

They may be thinking of hiring more cart pushers.

No. They were probably identifying the fact that you need help during the busiest time, the same thing you have identified already. Management can be slow to catch on to obvious things.

No don't judge yourself based on your ability to push carts.

They won't fire you without warnings

Maybe they though you were overworked and they are thinking about hiring another cart pusher to help you.