My nephew is better at speaking Engish than our own native language, which is Filipino. Any suggestions on how I can help him?

May I know which language is used more at home? If he is already speaking English in school, best to speak your native language at home. This way, he'll be exposed to both. If both domestic and education spheres only use English, it is very unlikely he will grasp his native tongue. This happened to my younger brother -- he is super fluent in English and sounds super awkward when he converses in our mother tongue. I also think that you should let your nephew watch tv shows in your native language. Children pick up languages by ear very fast and watching tv actually helps. I, myself, learnt speaking languages other than English and my mother tongue by watching tv and reading subtitles.