I was thinking of teaching my child English as his first language, do you think that would be okay, or would he have issues stuyding Filipino later on?

English speaking kids are somewhat perceived an intelligent one. I must admit, I too taught my daughter to speak english. In a way, speaking in english somewhat shortens things you may want to say vs saying it in Filipino. While I find it very nice, I also find it to be confusing on my daughter's side. When she mingles with other relatives whom cant speak english well, she's not responsive to them while they talk with her in filipino. In that regards, I also teach her filipino by conversing her using the local language. It is also beneficial when the child socializes with other kid with her own age, at least s/he can communicate with others be it in english or in filipino :)