Cool, once you submit your wallet app file fixes and I commit your pull request, it will show up here:
https://github.com/kenCode-de/smartcoins-wallet/blob/master/app/src/main/res/values-id/strings.xml

..and your app store descriptions in Indonesian will show up here:
https://play.google.com/store/apps/details?id=de.bitsharesmunich.smartcoinswallet&hl=id

#1 no, underscores are just used for variable names in the code. please type proper grammar and spelling.
#2 shorter is better. remember, this is a mobile wallet. i cannot commit your translation or qualify you for any reward if you mess up the xml tags, so please just edit the sentences and grammar where needed.

Please and thanx in advance :)