In dire help of understanding android architecture

Hello everyone, first time in developers forum here ^_^
Creating a clicking game for android, inspired a lot by the web game clicker heroes.
I'm facing a few methodical dilemmas and would like to know your opinions about those.
The application is going to be statical, a shop in third of the screen, while the other 2/3 will consist of a monster that can be clicked and some buttons that will pop-up a menu.

1. Fragments- i read a lot about these, not sure if i need one for the shop part, and if so how do i make it have tabs?

2. Saving data- the app is offline and i dont mind saving in local without it being encrypted, should i use SharedPrefrences or some other thing?

3. Calculate time from closing up to opening it or between pauses

4. If not fragments, how to replace widgets with one another?

5. Should i do everything in 1 activity? The app itself isnt requiring more

6. Each monster has unique picture and death animation, how to arrange and use it correctly in the resource file and java file?

Andddd finally im sorry im such a newbie, i just have a lot of passion and after hours of searching i havent found any guide that EXPALINS and not just shows how to use specific thing

Thanks in advance,

Else~^