I've heard the sentai will move to a new air time, it's true ?

Yeah, Super Hero Time is being pushed ahead by 2 hours or so, from 7AM to 9AM. It's when Kamen Rider Build starts airing

I just wanna certified that, but thanks.

Haha, I kinda liked it how he randomly began to shout short English phrases during the show. But was there any explanation on why he wanted to show his English skills, aside from looking cool maybe?

Not that I know of. I guess it was a random trivial thing the writers wanted to put in. :)
Regardless, all this talk makes me want a Figuarts of Gao Yellow... and how it will never come to be cause sentai Figuarts is obsolete at this point.

I think toei should reduce the numbers of team members, mostly currently doesn't have much screen time.

But that would mean less toys!

6 is the average number and Kyuranger's whole gimmick is more than the average amount

I think that, much like 3 man teams, the six man full team is slowly becoming an endangered species. The last Sentai to have 6 or less rangers was Go-Busters, or Gokaiger if you don't count the V-Cinema or Enter. The seventh ranger seems to be following a very similar path that the sixth ranger followed in the 90s.