twentyseventeen sub dropdown text width

Dear community,
I hope someone can help me. I found a lot of hints that where close to what I need but unfortunately I still couldn’t solve the problem:

On my website you see a submenu when hovering over “Veranstaltungen”
As you can see, some entries are that long, that they are displayed over several lines. There are two things I would love to have:

1. The width of the dropdown should automatically adjust to the longest entry. (I tried this code:

.sub-menu {
width: 500px;
}
) but it only changes the borders of the menu. the content is still displayed over multiple lines per entry.

2. The list of entries in that menu is quite long. would it be possible to show it in two collums.

thanks a lot for your help.

The page I need help with: [log in to see the link]