Welcome to the FORUM SxTxAxRxZ.First,to get ya started,please ditch the task killer & any battery saving apps,both for all the reasons that you've already read about here. Next step I'd recommend is downloading a Cache Cleaning app.There are plenty to choose from,you can't really go wrong with any of them.If you're not rooted,just pick one for non-rooted phones.
Once you've done those things,just read the 'STICKY' @ the top of the page & the one @the top of the 'ASCEND-ALL THINGS ROOT' page,if you haven't already.Just about every topic concerning this phone has been been addressed in previous threads,so,answers to some of your questions are probably answered there.
However,don't hesitate to ask when in doubt,we ALL had a 1st day here & questions to go along w/it!
Again,welcome to ANDROID FORUMS!