What you are saying in your subject and what you have said in Japanese are two different ideas. "I dare not speak Japanese" would be something like: 日本語を話そうとしません。 - literally means "I will not attempt to speak Japanese." The phrase you used in Japanese "日本語で話なしことができません。" has a small mistake too. You should say: 日本語で話すことが出来ません。　OR　日本語を話すことが出来ません。 The first phrase says "I can't speak in Japanese." while the alternative is "I can't speak Japanese. The difference is very slight, but expresses the same idea. I hope this is what you are looking for. Please be more specific next time about what you wish to get. Please ask questions.