What is Voltaire’s thesis in Candide? What should be my thesis for a critical essay?

What is Voltaire’s thesis in Candide? What should be my thesis for a critical essay?
I need to cover the whole book with my thesis, not certain parts of it. If anyone has any suggestions on even what to think about when writing a thesis that’d be great. I can take it from there.

I know that the book talks about plenty of things, and that he primarily reacts against Leibniz, but my teacher keeps telling me that really he is saying “work out in the garden” as opposed to all this philosophizing which leads to nowhere. I however find that he’s satirizing human foolishness in general, making fun of philosophy, church, armies, and love. I think he is saying that this world could be the best of all possible worlds if people actually went out and stopped doing things that don’t benefit people.

The book deals with the problem of evil and that was what Leibnitz was trying to explain in his theory of optimism. According to this theory, since God is all powerful and all-wise he must have created the best of all possible worlds. We cannot see the whole; if we could, we would see that what appears to be evil is really contributing to the general, overall good. Voltaire hated this theory because, among other things, he felt it could be used to justify the status quo and any and all manner of abuse, injustice and despotism. So, he set out to paint a world full of evil and set it against phrases like ‘best of all possible worlds’, etc. His idea is that we should stop trying to invent theories that are dealing with things beyond human understanding, because it takes us away from dealing in a meaningful way with the real problems that face us. At the end the little group begin by working individually and nothing good happens, but when they work together unexpected talents and results emerge. The idea is that if we work together in our garden, that is, work together in our little area of the world to make things better, we can achieve small but important results to make this world a better place. This far more valuable that theorising.