My first all grain session was not perfect.....but I still made beer!
The most important thing is that you learn from it and make appropriate adjustments for the next time. You now have a benchmark for your next batch.
You should be able to figure out YOUR actual efficiency based on your results from first attempt. Next time use YOUR efficiency to determine the amount of grains for the recipe. i.e. any recipe you find should have an assumed efficiency...if your efficiency is less then you will need to increase the grain bill (weight) proportionately so you get the desired OG.
You should also now know how much to adjust your strike water temperature next time to hit your target based on what happened in your first attempt. You now have actual "experimental" data to tell you how much heat your mash tun "sucks" away from the strike water, etc. (Amount of grains matters too.....). If you are not sure how to figure this out....BeerSmith software is helpful....or post your data if you wrote it down and we can help you.
Bad taste....could be lots of things....may not be from missed temp and efficiency....maybe you didn't let it ferment and condition long enough.....could also be a pH issue with your mash if your water has high or low alkalinity depending on what type of brew you made. (I had this issue with Stouts)
How far off were you on those things?
Also....did you write down everything you did so you can make adjustments next time,,.......and do you have BeerSmith software...??? Software makes it so much easier to make adjustments on your next batch.
Give us some more information and I am sure we can help you out.
Why didn't i give up when my first session wasn't quite right? Beacause I knew it was my first time and with experience...and help form folks on here....I would get smarter and better.....and now the beer gods smile down on me (most of the time....still make mistakes)
Don't give up...hang in there and learn from your mistakes...and have a beer!