Yes, that's normal, if you hold a stock for 3 days your buying power is restored to the amount next day. If you buy a stock and trade it the same day, it takes 3 days total to update buying power.
ya that's normal. When i was first starting out i read a book called Understanding Wall Street you can get it on amazon. it's not that expensive it's a big green book. It's an easy read and will explain the basics and a little more. it also have a little Wall Street dictionary in the back. It's the best book that i have read for getting the basics explained. I would advise pickin it up.
News 
Market Data 
Discover 
AI
