.btn_secondary{color:white;font-weight: 200;font-family: 'Arial', sans-serif;border: 1px solid white;border-radius:8px;padding:5px;text-decoration:none;  border: 1px dashed #999;text-align:center;}

      body{ padding:0px;
      margin:0px;
     
 }
    .banner {
  position: relative;
  width: 100%;
  height: 300px;
  background-image: url("https://www.ubpro.eu/B/uploads/sluzby/hodinovy-manzel.png");
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
  color: #fff;
 display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
}

.banner::before {
  content: "";
  position: absolute;
  inset: 0;
  background: rgba(0,0,0,0.44); /* průhledné ztmavení */
}

.banner > * {
  position: relative; /* aby text nebyl pod tím ztmavením */
}
@media (max-width: 768px) {
     .banner {
         width: 100%;
  height: 300px;
      }
    }