In der Presse wie auch im Fernsehen finden sich zunehmend Meldungen über die verheerenden Folgen des Spielens am Computer. Eine Klasse für sich Frauen unter sich Deutschland schafft sich ab. I found it really hard to explain what's the meaning of "sich" and what are rules about its usage, are there any rules which replies to my question?
sich etwas kaufen uses sich, but this has to be replaced by the appropriate personal pronoun, matching the earlier occurrence, which in the example case requires the plural uns. Sich is either singular or third person plural and would not match grammatically. The full list is: ich/mir, du/dir, er-sie-es/sich, wir/uns, ihr/euch, sie/sich.
Your question cannot be answered in general because the word "sich" is not always translated into one specific word when translating from German into English. Your own example illustrates this nicely: in German we say "setzt sich ein" but in English, you say "puts in" without a reflexive pronoun. On the other hand, in English you state " her contact lenses" with a possessive pronoun, while in ...
I always put sich after the verb i.e. in the third place. The verb then goes wherever it wants to go according to the placement of clause in the sentence. This makes it easy for me to realize early on whether the verb is reflexive or not.
reflexive - Where to place "sich" in an elaborate sentence? - German ...
As an English speaker learning German, "sich" is a very mysterious word. Consider these sentences from the schlagen entry in Duden: die Nachricht ist ihm auf den Magen geschlagen die Erk...