I wanted to ask my friend to do this but..

Other answers are giving you some kind of fun slang, but you don't have to try to master that if you don't want. You can make it as simple as "do you want to get two pizzas and share them?"

No frills question would be- Do you want to trade half of my pizza for half of your pizza? If you're both casually discussing two flavors that sound good you could throw out there- If you get pizza a, I can get pizza b and we can go halfsies.

I call it "halfsies" like "want to go halfsies on some pizzas?"

Other comments are correct but I'd ask my friends: "Wanna go halfsies?"

"I wanted to ask, but I didn't know how" Just ask as you can, nothing will happen they won't understand you

Exactly what you wrote in your post is fine: “do you want to cut the pizzas in half and swap them?”

Do you want to get two pizzas and split them?? That’s what I say to my roommate all the time lol.

Wanna split some 'za brah?

"Do you want to get an X pizza and a Y pizza, and each take half of each?" The first "each" refers to you and your friend, and the second "each" refers to the pizzas. You could also say "and each of us take half of each pizza", but native speakers will often simplify it. 🙂 Or you could say "do you want to get two different types of pizzas and split them?" There are honestly a lot of ways you could describe it.

Just whatever you do don't be so sad as to call sharing pizzas your "love language". That's so dumb.

It's look very nice. I like pizza.

I think you could have explained this well, don't let the fear of a grammar mistakes keep you from talking! It's better to say what you can with the language you know, and then look it up later, than to remain quiet and miss an opportunity to use English that is difficult for you.

Me and my boyfriend do this so often we just look at each other and say "half-and-half?" when ordering... but I feel this is a idiosyncrasy and not universally used lol. In our case, I assume it comes from ordering dishes like a curry here where they say "Would you like rice or chips?" and people respond "Can I do half-and-half?" meaning they get a smaller portion of both sides. I can't remember how we would have started the conversation initially but I think you already have a good grasp on how it works! Something as simple as "If I order X and you order Y, do you want to share?" Then you could just explain exactly what you mean by sharing "If I take half your pizza, I'll give you half of mine" or however much you want to share (we share almost all dishes so will often literally swap bowls halfway through meals haha). In short, there is no universally used term for this but it is a common occurrence and definitely one of my favourite ways to experience food :)

Do you want to swap halves?

"Do you want to swap half of your pizza with half of mine?"

Do you wanna cut our pizzas in half and swap? You said it already in your question. That is literally what I would ask.

“Do you want to go halves on two pizzas/flavours?”