Use the column-gap property to set the gap between the columns. You can try to run the following code to implement the column-gap property, with value 50px:
Example
<!DOCTYPE html>
<html>
<head>
<style>
.demo {
column-count: 4;
column-gap: 50px;
}
</style>
</head>
<body>
<div class = "demo">
This is demo text. This is demo text. This is demo text. This is demo text.
This is demo text. This is demo text. This is demo text. This is demo text.
This is demo text. This is demo text. This is demo text. This is demo text.
This is demo text. This is demo text. This is demo text. This is demo text.
This is demo text. This is demo text. This is demo text. This is demo text.
This is demo text. This is demo text. This is demo text. This is demo text.
This is demo text. This is demo text. This is demo text. This is demo text.
</div>
</body>
</html>