I'll be blunt. It's obvious you haven't Googled in the slightest. So I'd recommend you just buy a reputable Carplay-capable unit that fits your budget. A DIY

I'll be blunt. It's obvious you haven't Googled in the slightest. So I'd recommend you just buy a reputable Carplay-capable unit that fits your budget. A DIY CarPlay unit using a Pi will end up requiring a lot of research and will cost you more money than you'd spend just buying a pre-fab unit. I am not aware of any easy path to DIY CarPlay.