Im a first year student of physics. Because of coronavirus we have got online lessons, but my mechanic's lecturer doesn't like us, he didn't explain anything, just give us a problems to solve. I've got Landau-Lifshitz's book, but I even don't have enough caculus, to understand everything there. (there is the first and last equation, without derivation, I dont have even partial derivative in lessons [ofc., I learned it in my own, its not too bad, but Landau is still difficult]). Can you recommend me anything, that can help?