

この靴はサイズが小さいです。
もっと大きいサイズはありますか。
サイズが合わないので、交換したいです。
"サイズ" is in the lesson "Issues" (Level 45), along with 11 other useful words. LinDuo has 180 topic lessons like this one, 2,379 words in total. Every word has an illustration, a transcription and pronunciation in a female and a male voice. Just 10–15 minutes a day is enough to learn them all. Free, and works offline.