Ifyouwanttosay"IwanttoparticipateinanEnglishspeechcompetition"inChinese,youcansay"我要参加一个英语演讲比赛"(wǒyàocānjiāyīgèyīngyǔyǎnjiǎngbǐsài).InEnglish,youwouldsay"IwanttoparticipateinanEnglishspeechcompetition
If you want to say "I want to participate in an English speech competition" in Chinese, you can say "我要参加一个英语演讲比赛" (wǒ yào cān jiā yī gè yīng yǔ yǎn jiǎng bǐ sài).
In English, you would say "I want to participate in an English speech competition."