Android offers two basic methods to add special characters to your text:
5.7.1. Standard Access
For punctuation and symbols, use the default function by first tapping the
?123 key, and then optionally tap
5.7.2. Tap and Hold
Android’s on-screen keyboard contains additional options for some keys if you tap-and-hold them, for example tap-and-hold
U to get access to ü and other diacritics. This also works for some punctuation keys, such as the currency symbol showing other currencies.