Usei no CSS, Flex-box e Display flex. No HTML ul e li, classes

Hi!

Neat work, congrats =)

Here a couple of tips to improve it:

• Use are using mostly correct semantic tags, but you forget about main tag. Every page should contain one. In your case it could be .card.
• Also there no need to wrap links into form. The purpose of form tag to collect and send data to server.
• To better centering you can set min-height of the body to 100vh and use both flex align properties.

body {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
}

• Try not set explicitly height of your container element. In real projects the content could change time to time, so it's better to leave height by default.
• Use relative values for font size - rem. It's value depends on user's font setting. By default 1rem = 16px.

Overall, you did quite a good and accurate job. Keep doing =)