styles.css

* {
  padding: 0;
  margin: 0;
}

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

.header {
  padding: .5em;
}
.header__logo {
  height: 40px;
}
.main {
  height: 60vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  padding: 2em;
  background: url("./images/profesora.jpg") no-repeat;
  background-size: cover;
}
.main input {
  padding: .5em;
  width: 350px;
  margin: 10px;
  border-radius: 4px;
  border: none;
}

.gallery {
  padding: 1em;
  width: 90%;
  margin: 0 auto;
}
.gallery__title {
  text-align: center;
  margin: 1em auto;
}
.gallery__container {
  display: flex;
  flex-wrap: wrap;
}

.categories {
  width: 80%;
  margin: 0 auto;
  display: flex;
  padding: 5em 0;
  flex-direction: column;
  align-items: center;
}
.categories__list {
  display: flex;
  width: 100%;
  padding: 4em;
}
.categories__list--container {
  display: flex;
  flex: 1;
  flex-direction: column;
  align-items: center;
}

.categories__list li {
  list-style-type: none;
}
.categories__list li a {
  text-decoration: none;
  color: inherit;
}

.footer {
  display: flex;
  background: #fbf4f4;
  flex-direction: column;
  align-items: center;
  padding: 5em 0;
}
.footer__btn {
  background: #3eb060;
  padding: .3em 1em;
  margin: 1em;
  color: white;
  text-decoration: none;
  border-radius: 4px;
}