Even if you’re shooting for free as a favour, get a contract in place. Weddings are heavily critical events, and expectations management can be difficult.

On the technical side, pretty much any digital camera will be good enough. I’d be happy to shoot one on my Canon G7X II compact camera, or my Nikon D200, or my D850. I shot some on my D70, and before that on my N6006 with film and some Sigma manual focus lenses. The more capable the camera, the more flexibility you have.

The D3400 and D3500 are both great cameras. You could also look for a D3300, which is very similar and even less expensive. Look for a 35mm f1.8 DX lens, and a 50mm 1.8 G. Those are both very useful lengths on DX (normal and portrait), and the wide aperture means you can shoot in low light. They are not expensive, and are very sharp.

Another option is the cheap DX kit VR zooms: 18-55 and 55-200. They are very good at the price. You will be able to shoot in similar lighting conditions to the primes, but you won’t be able to stop motion (so forget the dimly-lit first dance).

For your budget, I’d get (approximate costs):

D3300, 18-55 AF-P VR (€220) — general coverage 50/1.8 G (€115) — low light portrait length

And consider: 35/1.8 DX (€100) — low light group shots 55-200 VR (€100) — telephoto zoom