Howdy Mirko,
I would love to help you with this.
It will take some fiddling with CSS to try and craft a fix there. The Avada folks might even be able to help, this looks like an issue their theme will be seeing with others users as well.
I tried to craft a fix for you here:
#tribe-bar-form.tribe-bar-mini div.tribe-bar-submit input[type=submit] {
font-size: .75em;
padding: 10px;
width: auto;
}
And that might work well. I have no way of knowing. In my Internet Explorer it is actually rendering great even without that CSS. Likely your client is on a different version than I am. Thus I am not actually sure if that will fix it, but it probably will. If you test with that and it fixes it, you might be interested in removing portions of it such as the font-size changes it makes, those might be overkill.
Does that all make sense? Did that work for you? Please let me know.
Cheers!
– Brook