How do you get sagging doors to close properly ?

Check the hinges, maybe some screws have come loose. Or the hinges may not be sturdy enough for the weight of the door itself and may have to be replaced.

Check the hinges, screws, etc. Here is a website with instructions. https://removeandreplace.com/2015/03/12/how-to-fix-a-door-that-is-sagging-or-hitting-the-door-frame/

I agree! Loose screws would cause the doors to sag. Sometimes the screw holes get enlarged over time from use. What you can do is get some longer screws, 2" to 3". Remove one screw at a time from the door frame and replace with the longer screws. Do the same to the door.

Make a collage of framed mirrors of various sizes on a wall to bounce the light around the room. Hang them starting 8-12 inches from the ceiling and as far as you can down to the floor. Accessorize using shiny objects, such as flower pots, toothbrush holders, etc. along with your mirror collection. Use white towels and bath mat(s).

And if the hinge screws have pulled the wood to loose to tighten them here is a trick to fix.

Buy a wooden dowel about 3/8 to 1/2" thick and cut to length of your hinge screws, drill out the striped screw hole using a bit the size of your dowel, and then glue your dowel plug with carpenters glue all around and hammer it in. Let dry and hour and then put your hinge back on. Pre-drill a hole for your screw with a smaller bit about halfway, then screw into your plug.