1. Why is trading forex better than trading stocks or futures?
Nothing,
it can be difficult because of high volatility and news coming each week. However, most folks like forex, since you can open a account with less than 1000$(cheap to everyone). And many believe they will be millionnaire performing EA or trading particular system.
Learning its the simple part( in 1 week-end you know nearly everything)...
Attempt to make money inside the first 6 month without loosing your first account!!!!
2. At the moment iam learning very much about candlesticks and that they are very based on gaps and sudden jumps.
Unfortunatelly in forex gaps and similiars rarely happen in resistance to futures or stocks. Why?
Candlesticks and that they are very based on gaps and sudden leaps is totaly untrue. Its just representation of price movement(Patern).

Sometime in Stocks you will have, what I call pause: Its when they stop trading the Stock because news annoncements or business alteration,etc.. It may also be other things.
In forex, It never stop except for week-end(Or vaions ). Most, if not all, of the time that the gaps will hapen on Sunday(Open time) or broker problem.
By the way in forex, the concept isn't like NASDAQ(Where they handle Bid and ask in a centralized place)(In forex is that the brokers that do so:Well assume to be the Bank;--RRB- )

3. Is there some platform where I can analyse futures and stocks? It should contain the very same features as metatrader. Or can I add stocks and futures to metatrader to simplify them?
Yes, few of them provide futures also.
You cannot add nothing to MT. You must open a account with a broker to be able to trade with them and also have Future or Forex whenever they provide them(or use a demo account). .