send button in one line with other buttons

Hey rixi,
Sorry for the late reply, and thanks for the link. As I understand your question you are referring to this form:

and you would like it to look like this:

you can do this within the form options, for each element go to the styling tab and choose the width you wish, for example 4 elements would fit in one line if each was 1/4 wide.

Another option would be to try this code in the General Styling > Quick CSS field or in the WordPress > Customize > Additional CSS field:

.avia_ajax_form .form_element_half {
    width: 24% !important;
}
.avia_ajax_form .first_form {
    width: 24% !important;
    clear: right !important;
}
#av_section_2 > div > div > div > div > div > form > fieldset > p:nth-child(6) {
	 width: 24% !important;
	 clear: right !important;
}

This is what I used to take the screenshot above.
After applying the css, please clear your browser cache and check.

Best regards,
Mike