Oh yeah I see, the typical timed emergency exit by Fox ;-)
Well since I really played all of your chambers with pleasure, would you mind doing me a favour and playtest my first one? If yes, it's the one with no name on my profile, and I gotta warn you, you not only need brains, maybe patience and a little skill (not too much), but foremost stamina, since it has A LOT of content, I admit.
That would be very kind.

All is fixed normally now !

TY you did all my chambers lol that's coo.l i will fix that

I like how your chambers have more content than it looks at first sight :-) There are always hidden rooms.
Well this one turned out easier than it looked. I'd suggest to remove the third button again. You can always correct the cube's position. Either you're inside and can access it with a portal or you're outside and restart from the beginning.
There might be a problem trapping yourself in the exit area. If you're dumb enough to displace the cube and then using both portals inside the glass area without having the cube... unlikely I know, but the last button should not only open the exit but also the way back :-)