how to put fields next to each other

I know what you mean. Been there. It’s not that obvious. When you hover over a row, you’ll see a double arrow in the middle.
Click on that to split the row in two containers.
Then you just put what ever field you want, in there.
You can divide a row into several boxes, not just two.

Works just fine on mobile. When viewed on a smaller screen, all fields will be positioned beneath each other.