shapes, gaps, and edge to edge

Site URL: https://www.gardenclubofoldgreenwich.org/plant-sale

I am trying to create a web version of a poster. The poster has a quadrilateral with text, and I managed to mimic the shape. I got the shape right (more or less) using triangles, but there is a gap between the top triangle and the block that I cannot figure out.

Also, iis there any way to get the whole shape to go from edge to edge? It's okay as it is, but it would be so much better edge to edge. 

<svg height="200" width="100%"">  
  <polygon points=" 0,200 1400,200 1400,0" style="fill:white">
</svg>
<div  style="background-color:#ffffff; vertical-align: middle; padding:40px 45px">   
<div style="color: #BA5776; font-family: 'futura';font-weight: 700;font-size: 5em; line-height: 1.2 !important;  text-align: center">Plant Sale
 Saturday May 14   </div>
<div style="color: #BA5776; font-family: 'futura';font-weight: 700;font-size: 2em; line-height: 1.2 !important; text-align: center"> (the day before Mother's Day) time place
</div>
  </div>
 <svg height="200" width="100%"">
  <polygon points="0,0 0,0 1400,200 1400,0" style="fill:white">
</svg>
 

Try adding to Design > Custom CSS

div#block-yui_3_17_2_1_1640767453119_1809 {
    margin: 0;
    padding: 0;
    width: 100%;
}
section#slanted-header>div {
    padding: 0;
    max-width: 100%;
    width: 100%;
}