loginUser(loginevent){
  loginevent.preventDefault()
  const target = loginevent.target
  const username = target.getElementById('username')
  const password = target.getElementById('pasword')
  console.log(username, password)
}

<form (submit)="loginUser($loginevent)">
    <input type="text" placeholder="Benutzername" id="username">
    <input type="text" placeholder="Passwort" id="password">
    <input type="submit" value="Login">
  </form>