Not really learning too much...
I didn't "master" the food category. This only taught me about 12 foods, 8 of which I already knew. For this to work, you're going to have to have more in-depth exercises while making the game go quicker. I have to use the cursor too often for the articles and it slows me down and gets boring.
You'll master the category on the site, but will not hold a mastery command over any of the categories presented. That's not the goal of this site. You will likely learn many more words from translation exercises and independent reading, as when you learned English originally.
Also, I don't use my cursor at all when I am on this site. You can simply press up and down to cycle through the drop boxes. On the picture clues, if you type the article then press space, the site populates the box with the article typed. For the multiple choice boxes, just press 1, 2, 3 appropriately.
Accents are a different story. I have a Mac, so all I have to do is hold down the letter key for a half second and I can then choose the appropriate accent. On the PC, there are other shortcuts you can use, or the ALT characters (hold ALT, type the appraise three or four digit representation of the character you want).