The modal form appears messy

Question

I need a little help. My modal form appears messy when I put inside my project. On the other hand, when I create a separate page, it appears perfectly as it should be. Follow the code:

input[type=text],
input[type=password] {
  width: 100%;
  padding: 12px 20px;
  margin: 8px 0;
  display: inline-block;
  border: 1px solid #ccc;
  box-sizing: border-box;
}

button {
  background-color: #4CAF50;
  color: white;
  padding: 14px 20px;
  margin: 8px 0;
  border: none;
  cursor: pointer;
  width: 100%;
}

button:hover {
  opacity: 0.8;
}

.cancelbtn {
  width: auto;
  padding: 10px 18px;
  background-color: #f44336;
}

.imgcontainer {
  text-align: center;
  margin: 24px 0 12px 0;
  position: relative;
}

.container {
  padding: 15px;
}

span.psw {
  float: right;
  padding-top: 16px;
}

.modal {
  display: none;
  position: fixed;
  z-index: 1;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  overflow: auto;
  background-color: rgb(0, 0, 0);
  background-color: rgba(0, 0, 0, 0.4);
  / padding-top: 60px;
}

.modal-content {
  background-color: #fefefe;
  margin: 5% auto 15% auto;
  border: 1px solid #888;
  width: 80%;
}

.close {
  position: absolute;
  right: 25px;
  top: 0;
  color: #000;
  font-size: 35px;
  font-weight: bold;
}

.close:hover,
.close:focus {
  color: red;
  cursor: pointer;
}

.animate {
  -webkit-animation: animatezoom 0.6s;
  animation: animatezoom 0.6s
}

@-webkit-keyframes animatezoom {
  from {
    -webkit-transform: scale(0)
  }
  to {
    -webkit-transform: scale(1)
  }
}

@keyframes animatezoom {
  from {
    transform: scale(0)
  }
  to {
    transform: scale(1)
  }
}

@media screen and (max-width: 300px) {
  span.psw {
    display: block;
    float: none;
  }
  .cancelbtn {
    width: 100%;
  }
}

<div id="id01" class="modal">
  <form class="modal-content animate">
    <div class="imgcontainer">
      <span class="close" title="sair">&times;</span>
      <img src="img/users.png" alt="users" class="avatar">
    </div>
    <div class="container">
      <label for="uname"><b>E-mail</b></label>
      <input type="text" name="uname" placeholder="Entre com o seu e-mail" required>
      <label for="psw"><b>Senha</b></label>
      <input type="password" name="psw" placeholder="insira sua senha">
      <button type="submit">Entrar</button>
      <label>
                <input type="checkbox" name="lembrar" checked="checked">Lembre-ne
            </label>
    </div>
    <div class="container" style="background-color: #f1f1f1">
      <button type="button" onclick="document.getElementById('id01').style.display='none'" class="cancelbtn">Cancelar</button>
      <span class="psw">Esqueceu a <a href="">senha?</a></span>
    </div>
  </form>
</div>

<button type="button" onclick="document.getElementById('id01').style.display='block'" class="cancelbtn">Exibir modal</button>