Bread basic question

Don't double the yeast, if anything halve it!  If you post your recipe we might be able to help better.  But some things to remember when making bread. 

Longer and slower first rising brings better flavor, but for that you need to use less yeast.  One loaf should have about half a package of yeast, at the most, for a regular speed rise.  But if you want a longer rising, use less.  More yeast is never a good idea. 

Then even if you follow the recipe (unless it's one of those that uses, say, 2 packages of yeast for one loaf, and then it's not a good recipe) , don't follow the timing .  The times for first rise and second rise (and eventually third rise) are only indicative.  Check frequently when you get close to the time.  Much will depend on the temperature of your room.  Heat makes bread rise faster, cold slower. 

Anyway, the rise is finished when it passes the finger test. 

Wet a finger and press it into the dough about half an inch,  then let go.  If it springs back and leaves no indentation, it's not risen enough, no matter how long you've left it.  If it caves in and leaves a dent all around the dent you made, then it's risen too much, and you have to press it down or reform it if it's the final loaf, and let it rise again, only this time will take much less time. 

If it leaves a dent more or less like you made, without filling in or filling in very slowly, then it's ready to pass on to the next stage, another rising or baking. 

If you let it rise too much in the last rising (when the braid is formed already) then it will collapse in the oven because you've exhausted the yeast, and the bread will be dry and cavernous.  Better reform it and if it's night already, reform it and refrigerate so it will be ready in the morning (the cold slows the process down considerably). 

Then make sure you knead it enough, so that it becomes very elastic under your hand, and looks almost shiny (satiny).  You should feel it resisting your pressure, like it was alive.  And a hard loaf can come from too much flour.  Try to add only as much as absolutely necessary not to make it stick. 

hope this helps.

Chana Ruth, have you tried adding some oil or honey to the recipe?  They will impede gluten chain formation, and will help the dough rise and result in a lighter crumb, if that's the texture you're looking for.

Siduri is correct; adding more yeast will speed things up, and make them harder to control.  You probably want ideally two rests - after the initial kneading (I usually hand knead for about 5min for challah) you want to cover it and let it rest until it's roughly doubled in size.  Then you can portion, roll and braid the dough, and let it rest again until the dough will lightly rebound after being poked (gently!).

If you mix the yeast, water, honey and flour together first into a dough AND THEN add in the eggs and salt, it will probably also help to achieve the texture you're looking for.  If the dough it too wet after adding the eggs, just knead on top of a handful of flour until each bit is incorporated, and the dough is no longer sticky to touch.

Finally, try baking at a lower temperature to avoid a hard crust - think 375 instead of 400.  Good luck!