Preselect a country code in booking form

Kommt drauf an welches Element du da verwendest!

Is it a custom-element? Or is it a Wix-Form.
Grab the ID of this element, or the id of one of the input-elements and generate your code, to prefil the inputs with your wished data you want.

$w.onReady(()=>{
	$w('#input1').value = "+49";
});

If you are using a DATASET, it already gets a little bit more difficult.
But still duable… (in this case an example with a DYNAMIC-DATASET → connected to a dynamic page).

$w.onReady(()=>{
	$w('#dynamicDataset').onReady(()=>{
		let curItem = $w('#dynamicDataset').getCurrentItem();
		let title = curItem.title
		let ID = curItem._id
		console.log(title);
		console.log(ID);
	});
	$w('#input1').value = "+49";
});

But if you are using already predefined stuff like wix-forms, you will have to go another way.