Okay, so, specifically to answer your question about that particular sentence... For starters, you're not breaking it up correctly. It should be read like this: (Many theories of truth) ARE LIKE (the neo-classical correspondence theory) The 'theories of truth' are being compared to 'neo-classical correspondence theory'. The author is saying they are the same. Next, the author discusses WHY they are the same: in being as much (theories of how truth-bearers are meaningful) as of (how their truth values are fixed). 'as much' here means the same as 'not only' or 'just as much'. 'as of' is a continuation of 'as much', in the same way that 'but also' is a continuation of 'not only' eg. 'not only do I like cats, but I also like dogs'. So the 'as much' and 'as of' is saying that 'theories of how truth-bearers are meaningful' and 'how their truth values are fixed' are the two important factors about both 'theories of truth' and 'neo-classical correspondence theory' which make them similar. So the explanation of the whole sentence is: Many theories of truth are the same as neo-classical correspondence theory because they are theories about how truth-bearers are meaningful and also about how their truth values are fixed. The key to understanding sentences such as this is being able to remove the objects from the sentence. Being able to recognise things such as 'theories of truth' and 'how their truth values are fixed' as topics will help, but this is very complicated language, even for a native English-speaker.

The tow ‘as’, two ‘of’, and ‘as much’, ‘as of’ makes me confused.

What are you asking exactly? It reads like a very dense academic essay.