I want to override sSaveComment function in Shopware engine/Shopware/Core/sArticles.php
since i want to replace at the place of (1 to 10 ) to (1 star , 2stars ,3stars) etc .
Changing the logic of functions is only possible with a custom plugin. Since this function has no events, it is only possible to change this function with a hook. There are three possible ways:
You can also use the hooks to make some custom things when the function is called (before/after).
But I guess it would be better (because of compatibility reasons) to change the appearance in the frontend. Changing the whole logic might cause incompatibilities with other extensions. Change the dropdown in frontend/detail/comment/form.tpl and use only values like 2,4,6,8,10...