Yup. Understanding what "desu" and "ka" mean and where they should go in a sentence is very basic, but VERY important. Japanese is generally a relatively easy language to learn. It's just the grammar that's a bit problematic. If you're a fast learner, good for you. If you're a bit slow, then well, you'll just take a while to learn. There are certain characteristics about the Japanese language that have to be noted, but you can only do that once your command of the language is... well, not too bad. It's not easy to explain how Japanese grammar works, see; you have to listen and read and talk a lot to get the hang of it. Things like that you just have to learn by yourself. It's not something we can explain in an entry.