Samsung
Turn Alternative Characters On or Off auf Samsung
The Samsung Keyboard reserves extra space for characters like the question mark, exclamation point, plus sign, multiplication sign, and the euro symbol. To make room for them, the keyboard swaps the letter row for a symbol row whenever you hold Shift or type an uppercase letter. If letters vanish exactly when you expect to type a symbol, the Alternative characters function is responsible.
This option lives inside the keyboard layout settings rather than the general system settings, which is why many users have trouble locating it.
To adjust it, open Settings ➔ General management ➔ Samsung Keyboard settings ➔ Layout ➔ Enable or disable Alternative characters.
Turning the toggle off keeps the letter row visible at all times and moves the extra symbols to the long-press menu instead. This helps when you frequently mix letters and numbers, for example when entering passwords or addresses. Turning it back on restores faster symbol access but temporarily hides letters whenever Shift is active.
If symbols still behave unexpectedly after changing this setting, check whether a third-party keyboard app is set as your default input method. The Samsung Keyboard settings only take effect while the Samsung Keyboard itself is active.