Let me start from the first question to the last:
"1. How to translate those small words:"
Follow Andreas' advice.
"2. How to set admin tool to default language"
You cannot do it. This is controlled by your browser settings. If you choose your default language in your browser to be Swedish, then you will see svenska selected in the language dropdown in admin.
'svenska' in the drop-down list which is correct, excpet that it would
be nice to have a capital 's';-). Is it a bug or is it taken from the
This comes from the .NET framework and we cannot fix it, sorry for this.
But isn't that going to be overwritten when applying the next service release?
Your newly created language-specific resources won't be overwritten until we decide to provide Sitefinity translated in your language out-of-the-box.
On a side note, it is always advisable to first backup your project before upgrading to a new version because occasionally there are problems during the upgrade.
Hope this helps!
the Telerik team