#outer {
  width: 100%;
  height: 400px;
  border-radius: 20px;
  background-image: url(https://media.istockphoto.com/id/1323032473/es/vector/panal-abstracto-de-vector-azul-moderno-con-fondo-de-monitor-de-coraz%C3%B3n-con-para-la.jpg?s=2048x2048&w=is&k=20&c=mXe4wSHc8kAcOXastbN9jhinrWGQX3vvJQUhDgvOcqA=);
  position: relative;
}
#inner-container {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  position: absolute;
  bottom: 0px;
}
.innertext {
  display: inline;
  position: relative;
  border-top-right-radius: 20px;
  background-color: #fff;
  padding: 5px 25px 0px 5px;
  font-size: 40px;
  color: #000;
}
.innertext:first-child::before,
.innertext::after {
  content: "";
  display: block;
  width: 40px;    /* double the radius */
  height: 40px;   /* double the radius */
  background-color: transparent;
  position: absolute;
  border-bottom-left-radius: 20px;
  box-shadow: 0 20px 0 0 #fff;  /* this to create the inverted corner border radius area, if you desire to change the positon you can control it via the first two values 0 20px which represents the x & y */
}
.innertext::before {
  top: -40px;
  left: 0;
}
.innertext::after {
  right: -40px;
  bottom: 0;
}
.innertext span {
  position: relative;
  z-index: 1;   /* to overcome the overlapping with the text */
}

<div id="outer">
  <div id="inner-container">
    <div class="innertext"><span>A test</span></div>
    <div class="innertext"><span>A test with a second line</span></div>
  </div>
</div>