Anyway, I found the Nokia Asha 308 which Amazon had not many Rezesionen. I ventured for the price and was not disappointed, fortunately.
Now the mobile phone and the dual sim function:
It can 2 different SIM cards are used. A SIM card is as usual firmly inserted inside underneath the battery. The second SIM card is inserted laterally through a slot. Moment during the operation, the second SIM card can be interchanged. In both you are always available, unless you phoned, surfing or you just send a SMS / MMS via one of the two SIM cards. In our case, it is very very improbable that my wife will be called on both SIM cards simultaneously. That's why for info: There is no call waiting function is when you make a Sim card and called on the other SIM card. Moment during the call, the other SIM card is just inactive. If you call someone on, always comes the query which SIM card to be used. There are 4 variables that can be set permanently.
Calls, SMS, MMS and data. Here you can choose whether always SIM card you want to query the Sim1 or Sim2 to genutz.
The mobile phone is very nice, well verabeitet by design and does not look cheap.
From handling her, it is very easy to use. The touch screen responds very well. The keypad lock is here as follows: Press a button on the right side, and then wipe the display left or right with your thumb. Widgets can be found on the start screen insert as well as the most important contacts eg law Mamas Phone number 0). Connect a headset via Bluetooth was not a problem.
It has for us the most important functions:
Dual Sim (2 SIM cards usable in a mobile phone)
It's got a camera
Music Player
Bluetooth
2GB micro SD card (expandable)
and much more
The following weaknesses we noticed:
In surfing the Internet is only possible via SIM network (no W-LAN / WiFi connection to the home router available)
Contacts are displayed only on the main SIM card.
To assign an image to the contacts, the contacts in the phone's memory must be. I find made stupid. In order not to have the contacts twice, I have deleted the contacts on the SIM card. I recommend here a backup of contacts (if the phone is sometimes broken)
You can assign contacts no ringtone. So-in-law a ringtone from the film "Game me the song of death" not going; o)
A ringtone of the SD card also choose not. You have to connect the phone to your computer and copy the MP3 in the ringtone folder in the phone memory. The space is very limited but a few MP3 find space.
Conclusion:
I have exactly what I needed. A Dual Sim Mobile Phone with simple handling and the most important functions. The dual SIM functionality is very good. Unfortunately, no Wi-Fi router but on the SIM card but possible. Clearly it is not a high-end smartphone, but it has in my opinion the most important turn. For the price absolutely fine.
Update: assign different ringtones is yet. See comment