.PostSingleModal {
  position: fixed;
  z-index: 10;
  top: 0;
  height: 100%;
  width: 100%;
  background: #fff;
  opacity: 1;
  overflow-y: scroll;
  margin-top: 56px;
  &.withSidebar {
    width: calc(100% - 260px);
  }
}

.PostSingleModal {
  position: fixed;
  z-index: 10;
  top: 0;
  height: 100%;
  width: 100%;
  background: #fff;
  opacity: 1;
  overflow-y: scroll;
  padding-top: 56px;
  &.withSidebar {
    width: calc(100% - 260px);
  }
}

Make modal the scrollbar using full width
Make modal the scrollbar using full width
