First brew day complete, need some feedback

Yesterday I brewed my first time and I would like some constitutive feedback on how to improve for my next batch.

I jumped i right to all-grain and most of the day went well. I used a kit from northern brewer, Extra pale ale kit.

I had my strike water at 175 and was able to hold my temp at 155 during the mash. I used around 12 liters for 8.5# of grain. When I drained my first running's I was surprised about the "low" amount of wort that came out. I batched sparged for 20 mins at 170 and drained that and still came up a bit short so I did a make shift fly sparge to get my 6 - 6.5 gallons for boil. After I boiled i came up short by a gallon/gallon and a half to my five gallons expected.

expected gravity after sparging 1.036, actual 1.025
expected gravity after boil 1.044, actual 1.050
projected ABV 4.12, projected to now be 5.1

My expected final gravity is 1.012

So what do you all think? obviously I didn't hit all the numbers that was expected. I may needed to have slow down my sparging maybe that would have helped. I also should have maybe added water to hit my five gallon mark.

So here is some questions I would like for next time
1. How long should I sparge?
2. if I come up short should I add water to the brew to get the expected volume?
3. Is it acceptable to add water after the fermenting process to get the five gallons? and what effect would this have on the beer?
4. How do I calculate my efficiency?

any other comments would be appreciated so I can become better. I realize its a learning process, but hey I am relaxing, not worrying, and soon be able to drink a home brew!!

First off, congrats on the first brew. I'm suprised to see when people jump into all-grain right away, but you won't be dissappointed.

As for your questions...

1. This depends on what method you're using. Fly sparging should take at least a half hour, but this is just my personal opinion. Batch sparging (which you'll probably get better efficiency with when first starting out) should only take about 10 minutes. I usually add my sparge water to the mash tun, stir really well, let the grain bed settle for 5-10 minutes and then crank the ball-valve open and let 'er rip.

2. I don't like adding water after the fact. If your gravity comes out high pre-boil, then yes, you can add water to get it where it needs to be. Otherwise, I usually run all my extra water through the mash to make sure I get all the sugars rinsed out.

3. No. Do not add water after fermentation has already been started. You're just diluting the beer at this point. If you want to add water, it needs to be done before adding yeast. You also risk infecting the batch the more you mess with it after fermentation.

4. I suggest looking into a brewing calculator. I use BeerTools Pro, but there are plenty of others out there. These will calculate your efficiency as well as giving you the correct amount of water to add to your mash.

All-grain introduces processes that take a few batches before you're consistent. There are a few brewing software which will do a lot of the math for you, so that things are somewhat predictable. I made a spreadsheet to do these calculations for me. Some good calculators can be found here: http://www.brewersfriend.com/ and a lot of equations for predicting volumes, gravity etc etc here: http://www.grimmysbeer.com/ If you scroll 2/3 - 3/4 of the way down, you'll find a lot of the stuff you're looking for, in terms of predicting how much wort you'll run off, etc.
To answer your questions:

1. If you're batch sparging it doesn't really matter how long you sparge, as long as you give it enough time for the remaining sugars to diffuse into the water. I typically see a lot of activity in the mash tun when I dump in the sparge water (lots of bubbles, swirling) and I usually just wait until that stops. 10-20 min is plenty of time to wait before draining. You can drain as fast as your system allows.

2. I wouldn't add water. Personally, I'd rather have less beer that tastes like it should than the right amount of beer but watered down. If, however, you're shooting for a low-gravity beer and you end up way high, I guess it could be done. Plus, 1.050 isn't outrageously high.

3. I'd be even less inclined to add water after fermentation. It'll just water down your beer.

4. Efficiency is one of those things that is often misunderstood. I'd recommend reading Kaiser's writeup here: http://braukaiser.com/wiki/index.php?title=Understanding_Efficiency but the above website with the equations has some simple calculations for efficiency as well. Understanding the difference between conversion and lauter efficiency is a big step towards identifying problems in your process and improving your beer.

Overall, it looks like you did well for a very first brew AND first all-grain. Have fun!