[TOKU] Question about Japanese culture

Hey guys. First of all, I'm kinda new here. Little new to Sentai. Grew up watching PR. I have been working my way through Gokaiger and LOVE it. My question pertains to things I have noticed while watching. I don't know much about Japanese culture, so why is some of the dialogue spoken in English? I noticed Luka particularly says stuff in English a lot. And stuff like finishing moves, or "Gokai change". Barizorg saying "yes, boss", etc.



Also, if you all can recommend some other Sentai series that are good for beginners I'd appreciate it!