não aparece o footer!

quanto estou abrindo no mobile o footer fica atras do textarea, alguem poderia me explicar oq ta acontecendo e uma possivel resolução? HTML:

/*tive que tirar se não nao cabe aqui no forum*/

<footer>
            <img src="logo-matheus.png" class="logo-matheus">
            <p class="copyright">&copy; Copyright Matheus H. Paulino - 2023</p>
 </footer>

CSS:

body{
  background-color: #E5E5E5;
  width: auto;
  height: auto;
}

header{
  width: auto;
  height: auto;
  margin-left: 40px;
  margin-top: 20px;
  margin-bottom: 40px;
}

main{
  display: flex;
  margin-left: 80px;
  margin-bottom: 50px;
}

.input-texto{
  margin-top: auto;
  background-color: rgba(255, 255, 255, 0.8);
  margin-bottom: 10px;
  font-weight: 400;
  font-size: 32px;
  line-height: 150%;
  border-radius: 10px;
}

textarea::-webkit-input-placeholder {
  top: 168px;
  font-family: 'Inter', sans-serif;
  font-style: normal;
  font-weight: 400;
  font-size: 20px;
  line-height: 150%;
}

textarea::-moz-placeholder {
  top: 168px;
  font-family: 'Inter', sans-serif;
  font-style: normal;
  font-weight: 400;
  font-size: 20px;
  line-height: 150%;
}

textarea::-ms-input-placeholder {
  top: 168px;
  font-family: 'Inter', sans-serif;
  font-style: normal;
  font-weight: 400;
  font-size: 20px;
  line-height: 150%;
}

.mensagem {
  position: absolute;
  font-size: 16px;
  font-weight: bold;
  width: 400px;
  height: 500px;
  left: 820px;
  top: auto;
  background-color: rgba(255, 255, 255, 0.8);
  box-shadow: 0px 24px 32px -8px rgba(0, 0, 0, 0.08);
  border-radius: 10px;
  background-image: url("boneco.png");
  background-repeat: no-repeat;
  background-position: center;
}

.copiar{
  /*tive que tirar se nao nao cabe aqui no forum*/
}

.nenhuma-mensagem{
 /*tive que tirar se nao nao cabe aqui no forum*/
}

.texto-deseja-criptografar{
   /*tive que tirar se nao nao cabe aqui no forum*/
}

.botoes{
  display: flex;
  flex-direction: row;
  margin-top: 20px;
}

.encriptar{
  margin: 50px 0 50px 0 ;
  align-items: center;
  flex-direction: row;
  align-items: flex-start;
  font-family: 'Inter', sans-serif;
  font-size: 16px;
  font-style: normal;
  color: white;
  padding: 24px;
  gap: 8px;
  width: 328px;
  height: 67px;
  background: #0A3871;
  border: 1px solid;
  border-radius: 24px;

  order: 0;
  flex-grow: 0;
}

.desencriptar{
  margin: 50px 0 50px 0 ;
  margin-left: 24px;
  box-sizing: border-box;
  align-items: center;
  font-size: 16px;
  font-family: 'Inter', sans-serif;
  font-style: normal;
  color: #0A3871;
  flex-direction: row;
  align-items: flex-start;
  padding: 24px;
  gap: 8px;
  width: 328px;
  height: 67px;
  background: #D8DFE8;
  border: 1px solid #0A3871;
  border-radius: 24px;
}
.esclamacao{
  float: left;  
  margin-right: 8px;
  margin-bottom: 17px;
  width: 16px;
  height: 16PX;
}
.informacao{
  font-size: 12px;
  margin-bottom: 17px;
  font-family: 'Inter', sans-serif;
  font-weight: 400;
  line-height: 150%;
}

footer {
    text-align: center;
}
.copyright{
  font-size: 11px;
  font-family: 'Inter', sans-serif;
  font-weight: 400;
  line-height: 150%;
}

.logo-matheus{
  margin-top: 100px;
  width: 90px;
}


@media (max-width: 480px) {
  body {
    width: 100%;
  }

  header {
    margin-left: 20px;
    margin-top: 10px;
    margin-bottom: 20px;
  }

  main {
    flex-direction: column;
    margin-left: 20px;
    margin-right: 20px;
    margin-bottom: 30px;
  }

  .mensagem {
    width: calc(100% - 15px);
    height: 400px;
    left:5px;
    margin-top: 20px;
  }

  .nenhuma-mensagem {
    margin-top: 350px;
    margin-left: 20px;
    width: calc(100% - 40px);
  }

  .texto-deseja-criptografar {
    margin-top: 20px;
    margin-left: 20px;
    width: calc(100% - 40px);
  }

  .botoes {
    flex-direction: column;
    margin-top: 20px;
  }

  .encriptar {
    margin: 20px 0;
    width: calc(100% - 40px);
  }

  .desencriptar {
    margin: 20px 0;
    margin-left: 0;
    width: calc(100% - 40px);
  }

  .input-texto {
    font-size: 18px;
    margin-left: 0px;
    margin-right: 0px;
  }
  .copiar {
    margin-top: 450px;
    margin-left: 130px;
    }

  .footer {
    position: relative;
    margin-top: 50px;
    padding-top: 20px;
    padding-bottom: 20px;
    text-align: center;
  }

  .footer .logo-matheus {
    width: 60px;
    height: 60px;
    margin-right: 5px;
  }

  .footer .texto-footer {
    font-size: 14px;
  }

  textarea::-webkit-input-placeholder {
    top: 114px;
    font-size: 16px;
  }

  textarea::-moz-placeholder {
    top: 114px;
    font-size: 16px;
  }

  textarea::-ms-input-placeholder {
    top: 114px;
    font-size: 16px;
  }
}