This game is pretty easy to understand, but I'm going to give a quick explanation of what to do + I'll link the answer key here if anyone needs it.

You choose a category of words and you will be given a certain amount of blanks. When all the blanks appear, a word in Japanese will appear above the blanks. You need to figure out what the word is in English and choose the correct letters to fill in the blanks. Speedrun timing starts when you choose a category, timing ends when you complete the 10th word.

You can use this GameFAQs guide to see what all of the possible answers are: https://gamefaqs.gamespot.com/nes/578220-popeye-no-eigo-asobi/faqs/41952