4 weeks is not a lot of time. Japanese is nothing like English or French (which are closely related), so you won't really be able to use anything that you have learned.
If you haven't done so already, you should memorize the kanas (which doesn't take long), and know at least the 100 or so kanji on the JLPT 4 test, as well as the vocabulary. You can find these online by going here:
JLPT Level 4 Study Page
Knowing the kanas, kanji, and vocabulary won't help much at first, but after you spend some time here, you'll get to hear them in actual use, and get a chance to use them yourself. 4 weeks is not really time to learn anything new, but should be enough time to learn to use what you are studying
now.