Many European languages use letters with diacritical marks, such as the umlaut in German, the cedilla and circumflex in French, and the tilde mark in Spanish. To type a diacritical mark (such as an accent mark or umlaut), you can tap and hold on the base key to show more options. For example, hold down on the A-key for Ä or Á.
To type a symbol such as an apostrophe or hyphen, you will find these by tapping the 123 key on your keyboard on mobile. This will open a keyboard of numbers, punctuation marks, and special characters.