Go ahead and change things. This is a wiki, after all :-) Regarding translations, the mediawiki translate system is quite smart, so you won't mess up translations as long as you don't touch the translations tags (the <!--T:...> things). Don't make changes to the tags themselves (You can change the text, that they are attached to), don't create new ones; and if you want to move content around move the tags along with the text you move.
If you should make mistakes it is easy to revert the changes, so there is really no danger. If you want to know more we have pages for contributors here.
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