How to change the keyboard font size on Huawei P30?

Hello,

1) The first thing you can do is to place the smartphone in landscape mode instead of portrait: This will widen the keyboard and reduce the likelihood of errors.

2) To better distinguish the keys, enable key outlining. The process obviously depends on the keyboard you are using.
For the Google keyboard (Gboard):
- Click on the gear icon for settings:
- Go to Theme
Click on the active theme (marked with a V)
- Enable Key outlining and click on Apply

Notes:
1) This key outlining is available for all keyboards.
2) You can change the keyboard by going to the smartphone settings:
For Samsung: Settings > General management > Language and input > Default keyboard
3) I see that you specified that the smartphone is a Huawei P30.
This may interest you.