Multicolumn contact form fields

I have setup my contact form like this:
Now I want to have a form that looks like this:

| Dropdown               |
| First Name | Last Name |
| Message                |
| Submit Button          |

is something like this possible?
The most helpful information for me was this here:

but I have no glue how to implement a wrapper for 2 fields (will create a row in the template with 2 columns).