I think keeping it in your personal wallet is actually no problem because it is your right, but in my opinion if you invest only to sell it when the price is high why not keep it on an exchange site so that it makes it easier for you to sell it straight away when you buy to keep it, I know that Keeping it in your wallet is safe, but there are no benefits when you hold it in your personal wallet.

So far the Freebitcoin site may be said to be a safe site and you may also think that money placed with a third party will not be safe, but if you save it on this freebitcoin site you will probably get many benefits compared to keeping it in your wallet, for example WOF and other benefits because You lock it too, but I also don't force it because any decision is up to you