I am currently in the process of teaching myself QFT. It is not an easy task. I have armed myself with many of the standard textbooks. However, I am slow learner. I get stuck on a thousand different terms which I don't understand, and a style of 'mathematics speak' which loses me 95% of the time. There are so many gaps in my knowledge that if I were a ship I would be at the bottom of the ocean. What I really need is a book called 'QFT for Morons'. That's a bit harsh but 'QFT for dummies' doesn't quite express it clearly enough and besides there isn't such a book as far as I can find.
Any suggestions of resources or books that might help? What I am really looking for is the one that explains QFT like you were talking to a five year old. Perhaps I am asking the impossible.
I will add a bit more of a specific question here. I have learnt that there are groups and non-abelian Lie groups like SU(2) etc., and then there a lagrangians, as well as a few other things like operators and states. So a really dumb question is how are the lagrangians derived? Are they determined by the group? I am also confused because I understand some of the groups like SU(3) are used for different things in QFT. I feel compelled to appologize for my ignorance but I am determined to make so more progress with this. The problem when one is teaching oneself is you don't know which is the most fruitful path to follow.