Correct me if I'm wrong I just think that when you buy high but you sell it in low price I think you lose, right?
Yes, you lose if you Sell your coins below your Buy price. Lets say you bought at 0.1 BTC, price dropped yo panicked and sell at 0.08 BTC thats a loss, but it also depends on the current market price of BTC.
What if you you buy it at a higher price then the price falls on the next days or week will you loss something?
Yes you lose but you have the option not to sell while the price dropped below your Buy price, hold on to it until the price recovers, then Sell. There are times it may take more than 1 month before the price meets your target goal.
What if you'll just hold for it and wait for the price to bounce back?
If you have the patience to wait for the coin to recover then hold is the answer to recover your loss but if you see another opportunity to earn and you see you could earn more and at the same time recover your loss then sell and buy that coin that you see have a greater potential.