How can I withdraw the money (profit, because I want to keep the amount invested), is the localbitcoins site reliable? Is there any way, some regulatory body that can help me in case of any fraud?
Try to research if there is a local exchange in your area. It's way more convenient since it will touch your local payment system there that will give you a less hassle withdrawal. Im sure there is. If there's none then you have no choice but to deal with global exchanges. But like I said, Im sure there is.
And most of local exchange are legit company so at least you will be comfortable using them.
How does the wallet work? Which wallet is the simplest to use? How to invest? Is it necessary to sell bitcoins (I saw that the value is lower than for purchase) to move the bitcoins? Is there any booklet for small investors here in Brazil?
Wallet will act as your storage for bitcoin. It can be classified as web wallet, desktop wallet, hardware wallet e.g offline wallet. It's a basic thing to learn so you might hit your precious search bar there for much detailed information. Don't worry you will found it interesting to read since you want to own one.
How to invest? After finding an exchange (preferrable local one) , refer to their deposit page and understand all the details here. Methods are varied per exchange so you need to read it by yourself.
If you think it's necessary to sell then sold it. If you need money sold it. If you want to take advantage of the price increase, sold it. If you eye for long term then hold it instead. It's your decision at the end of the day.
