Elements overlap ignoring z-index

I developed a left menu, which overlaps the main content, but some elements of the main content overlap the menu ignoring the z-index. I guess the problem are the relative positioning of both elements:.

Here the code, it is just a part in order to reproduce the problem:

body {
 margin: 0
}

.root {
  margin: 0;
  padding: 0;
  height: 100%;
  display: flex;
  flex-direction: column;
}

.bar {
  padding: 0.5em 1.5em 0.5em 1.5em;
  align-items: center;
}

.content {
  display: flex;
  flex: 1;
  overflow: hidden;
  position: relative;
}

.sidebar {
  position: absolute;
  top: 0;
  left: 0;
  height: 100%;
  background-color: black;
  color: white;
}

.page {
  flex-grow: 1;
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  background-color: yellow;
}

.sub-title {
  display: flex;
  gap: 1em;
  align-items: center;
  padding: 1.5em;
  text-transform: uppercase;
}

.page-content {
  display: flex;
  flex: 1;
  flex-direction: column;
  overflow-x: auto;
  padding: 0 1.5em 1.5em 1.5em;
}

.page-content-wrapper {
  flex: auto;
}

.heading {
  display: flex;
  align-items: center;
  margin-bottom: 1em;
}

.search-wrapper {
  flex: auto;
}

.search {
  display: inline-flex;
  align-items: center;
  position: relative;
}

input {
  padding: 0.75em 2.75em 0.75em 1em;
}

svg {
  width: 1.25em;
  right: 1em;
  position: absolute;
}

<div class="root">
  <div class="bar">Title</div>
  <div class="content">
    <aside class="sidebar">
      <ul>
        <li>item menu</li>
      </ul>
    </aside>
    <div class="page">
      <div class="sub-title">Subtitle</div>
      <div class="page-content">
        <div class="page-content-wrapper">
          <div class="heading">
            <div class="search-wrapper">
              <div class="search">
                <input type="search" placeholder="Search configurations" value="">
                <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24">
                  <path d="M15.5 14h-.79l-.28-.27C15.41 12.59 16 11.11 16 9.5 16 5.91 13.09 3 9.5 3S3 5.91 3 9.5 5.91 16 9.5 16c1.61 0 3.09-.59 4.23-1.57l.27.28v.79l5 4.99L20.49 19l-4.99-5zm-6 0C7.01 14 5 11.99 5 9.5S7.01 5 9.5 5 14 7.01 14 9.5 11.99 14 9.5 14z"></path>
                </svg>
              </div>
            </div>
          </div>
        </div>
      </div>
    </div>
  </div>
</div>

I am sure that the problem is the two relative elements, but I don't know how to fix it.

Please need help. Thanx.

Solution

If I understood your problem correctly, what you need is to add to .sidebar{...} the following format: z-index: 1; And this is how it will look:

body {
 margin: 0
}

.root {
  margin: 0;
  padding: 0;
  height: 100%;
  display: flex;
  flex-direction: column;
}

.bar {
  padding: 0.5em 1.5em 0.5em 1.5em;
  align-items: center;
}

.content {
  display: flex;
  flex: 1;
  overflow: hidden;
  position: relative;
}

.sidebar {
  position: absolute;
  top: 0;
  left: 0;
  height: 100%;
  background-color: black;
  color: white;
  z-index: 1;

}

.page {
  flex-grow: 1;
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  background-color: yellow;
}

.sub-title {
  display: flex;
  gap: 1em;
  align-items: center;
  padding: 1.5em;
  text-transform: uppercase;
}

.page-content {
  display: flex;
  flex: 1;
  flex-direction: column;
  overflow-x: auto;
  padding: 0 1.5em 1.5em 1.5em;
}

.page-content-wrapper {
  flex: auto;
}

.heading {
  display: flex;
  align-items: center;
  margin-bottom: 1em;
}

.search-wrapper {
  flex: auto;
}

.search {
  display: inline-flex;
  align-items: center;
  position: relative;
}

input {
  padding: 0.75em 2.75em 0.75em 1em;
}

svg {
  width: 1.25em;
  right: 1em;
  position: absolute;
}

<div class="root">
  <div class="bar">Title</div>
  <div class="content">
    <aside class="sidebar">
      <ul>
        <li>item menu</li>
      </ul>
    </aside>
    <div class="page">
      <div class="sub-title">Subtitle</div>
      <div class="page-content">
        <div class="page-content-wrapper">
          <div class="heading">
            <div class="search-wrapper">
              <div class="search">
                <input type="search" placeholder="Search configurations" value="">
                <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24">
                  <path d="M15.5 14h-.79l-.28-.27C15.41 12.59 16 11.11 16 9.5 16 5.91 13.09 3 9.5 3S3 5.91 3 9.5 5.91 16 9.5 16c1.61 0 3.09-.59 4.23-1.57l.27.28v.79l5 4.99L20.49 19l-4.99-5zm-6 0C7.01 14 5 11.99 5 9.5S7.01 5 9.5 5 14 7.01 14 9.5 11.99 14 9.5 14z"></path>
                </svg>
              </div>
            </div>
          </div>
        </div>
      </div>
    </div>
  </div>
</div>