Having issues with Css design

I suck at using CSS, so i got this form to use in my project, but when i added it to my project the design seems bad...

Is my CSS code for the form

   /* SignUp form */
.formInputs {
  width: 100%;
}

.shadows {
  -moz-box-shadow: 0 4px 6px 0 rgba(32, 33, 36, 0.28);
  -webkit-box-shadow: 0 4px 6px 0 rgba(32, 33, 36, 0.28);
  -o-box-shadow: 0 4px 6px 0 rgba(32, 33, 36, 0.28);
  box-shadow: 0 4px 6px 0 rgba(32, 33, 36, 0.28);
}

.formInputs input[type="text"],
.formInputs input[type="password"],
.formInputs input[type="date"],
input[type="submit"] {
  width: 230px;
  height: 30px;
  padding: 5px;
  border: 1px solid #eee;
  border-radius: 8px;
  margin: 10px;
}

input[type="submit"] {
  background: purple;
  padding: 10px;
  color: #fff;
  height: 40px;
}

.myFormbase {
  margin: 10px;
}

.webAppContainer {
  width: 100%;
  height: 100vh;
  position: absolute;
  top: 0;
  right: 0;
  border: none;
  background: rgba(0, 0, 0, 0.6);
  bottom: 0;
  left: 0;
}

.webAppWrapper {
  width: 500px;
  border: none;
  margin: 80px auto;
  position: relative;
  background: #fff;
  overflow: auto;
}

.formContainer {
  text-align: center;
}
.myheader {
  padding: 12px;
}

How do i set the form to be on a plain background without affecting the footer and the navigation bar?