While doing temple map closing

is it like expected? I cant run temple if Ill be missing every map
also explanation on how to do temple is totally unclear I have no idea how to finish it at least once with boss

Vaal temple is a separate area, if you leave the map, its instance is empty and will be closed after a while as all instances are. It's complete bullshit in this case, but that's how it is.

Simply finish the area/map and then go to the temple via the next area waypoint or from your hideout. As soon as the 6th crystal has been lit anywhere, the temple is available and it stays available until you run it, no matter what you do in between.