The zones don’t recalculate every time you add a trace, remove a trace, or move a trace that intersects with the zone. You need to manually recalculate the zone with the b key. To avoid having to regenerate the zone all the time you can select the button in the left-hand tool bar to hide the zone fill while you work, letting you recalculate the zones only when you need to check connectivity (to make sure you haven’t cut off pads that want to be connected to the zone) yet still see what you are doing.
There are some really well written FAQ entries on this site that you can access with the FAQ link in the right of the header bar of this website. But, that category isn’t well organized. One of the items there is an index of FAQ entries organized by category. You may want to bookmark this item so you can refer to it while learning.