For now I hold them in Bittrex Wallet hope will not be scammed
No, Read:
Quote from: LTU_btc
It's not recommend to use exchanges as a wallets. You should keep coins/tokens in a wallet where you have full control of your funds. You shouldn' keep big amounts of money on exchanges because there are many stories about hacked exchanges, locked funds of users and etc.
Also, are you familiar with the huge amount of scam accusations and complaints about them?
Quote
like for myethereum , freewallet ect wallets ripped last months agp with phishing , hackij .. Just run MEW locally: How To Run MyEtherWallet Offline and Locally
Freewallet is hosted wallet hence, you are not fully in control of your funds