In fact it is perfectly possible to simply say: "I feel like an ice cream." ("eating" is not really necessary as, of course, that is what you usually do with an ice-cream anyway...). However, the risk of saying it like this is that somebody in might jokingly comment "Well you look like one, too!" This is a tired old joke still sometimes heard in the UK.

Sooo TRUE LOL! ;)))))))

"I feel like eating ice cream" "An" means "1" and implies there can be more than 1 ice cream. It's hard to imagine what "2 ice creams" look like because the words "ice cream" just describe the substance in general, not a specific amount of it. We wouldn't say "an ice cream" unless talking about a specific object, because. For example: "I want to eat an ice cream cone". In this case it's obvious what 2 ice cream cones would look like. However, we do say "an ice cream" if it's obvious that we're talking about a specific amount of ice cream. For example, when I order food I can ask "can I have an ice cream?" or "can I have 2 ice creams?" because their menu has items with ice cream and the waiter already knows what they are. So it is implied that I'm saying "an ice cream cone" or "a bowl of ice cream" or "a scoop of ice cream". Hopefully that made sense. People will still understand what you mean if you say "I feel like getting an ice cream", it just sounds odd.

what is it eating? I don´t understand :c

I would say the verb “to eat“ really doesn‘t match well with ice cream. No doubt people say „I feel like eating an ice cream“ (you‘d rarely say „to eat“ by the way) because when you think about it you really don’t „eat“ ice cream. It’s not something you chew up and swallow. But, then you don’t drink ice cream either, because it usually melts in your mouth and then is swallowed, but there is no chewing involved. And ice cream doesn‘t start out as a liquid. So, which verb to use? In would always just say „I’d like to HAVE an ice cream.“ I suppose you could say „I’d like to partake of an ice cream“ but that sounds awfully stuffy, and sounds kind of awkward and strange. Little kids might say they want to eat ice cream, but that’s just little kid talk. Just say „I’d like to have an ice cream“ and you’ll be fine about 99% of the time.