Because literally in banking system for example, if you have $5000 that will be the value in 3 to 5 months and will add a little interest in it so my question is- I don't fully know how bitcoin works. Is it the same way with the banking system? Will I get more value or less value in future times?
Don't invest yet until you fully understand everything about Bitcoin, you could possibly lose the value of your investment or you can have the ten-time profit of what the banks can give you, but the most important here is understanding the market, that is why here in Bitcointalk we strongly advise all new investors to only invest what they can afford to lose.
If it's your life savings and for emergencies don't put everything in Bitcoin investment, there might come a time that you need to trade and the market is down and you lose the value of your investment, so think twice before investing.