change max columns for cross selling products

I want to Change the max. columns for cross selling products.
As you can see on my site https://www.agoshop.at/shop/ago-quart-der-algen-und-moosentferner/ago-quart-50/ I use there 3 cross selling products but I have space on the right side. Therefore I want to Change the columns to 3 and I think it will be used 4 columns.
Hope somebody can help me.
kindly regards

Additional Information.
I have selected 4 items but only 3 will be desplayed. How can I present all 4 items and 3 in one line.
kindly regards