Sotah 7:1 gives a list of things that are said in any language, including the Sh'ma and the t'filah. Several commentaries I've seen explain that these texts are so important that you need to understand what you're saying. Yet I know many people who are not fully fluent in Hebrew who, nonetheless, say these in Hebrew, either in deference to tradition or because they are trying to learn the Hebrew and expect to one day understand it. (This latter group includes baalei t'shuva, converts, and children.)
Are we required to 100% understand the words we're saying in these cases, and some should pray in their local languages rather than Hebrew? Or is it enough if we understand the gist of what we're saying -- this paragraph is about X, this paragraph is about Y, and so on, even if we don't understand the words exactly?