I have 13$ worth of btc.i dont understand what will happen,if i holding this btc for a long time ?
It just depends on how long you hold and what the price is when you sell or trade for goods.
It could be worth $1 or it could be worth $10000
It could be good to hold your bitcoins for a long term, keep in mind there are more risks that you have to take to do this but it will also maybe be more profitable at the end, A long term investment can let you gain a lot of money if the bitcoin grows to a very large currency.
Yes true I think it has a risk aswell but it's very minimal we know what bitcoin can reach and it will reach that if all goes well.
The most important thing is to have as many coin as possible so you can profit from value increase as much as is possible.