Idea is good, the implementation is not good

I need a portable keyboard that I could use for Android and iPad.
Positives:
-Easy, compact, easy coupling, some useful features for Android (Samsung Galaxy S4 Active) I accidentally discovered (there is no operation Introduction): eg keyboard language can be changed by pressing a button, the screen can be turned off by pressing a button, between active programs can be connected, etc.
Negatives:
- Get used and dirty keyboard.
- A button is defective.
- There is no Bedinungsanleitung for iPad and Android. Many combinations do not match the label and must be laboriously "palpated".
- There are dropouts when typing
I have returned to the keyboard and will look no further.

Addendum.
I have ordered a better product and tested: iClever i25 3-in-1 Ultra Slim Mini Bluetooth 3.0 keyboard (QWERTY)
The keyboard of iClever is simply superior: no long searches of @ and SS signs, work all printed codes. You can easily switch between iPad, Android and Windows layouts.
There is a brief guide for iPad, Android and Windows. The keyboard of iClever acts valent.
Nachtrag2.
Devices approachable - Unfortunately the keyboard of iClever is after 2 days not more for Bluetooth.
Conclusion: better to buy a branded product. time is money.