Is there any secure method to keep or to withdraw the bitcoin to cash? Perhaps any system/programs or pen drive? Please enlighten.
You have asked two things here.
Secure Method to Keep Bitcoins1- Keep your bitcoin in Hardware Wallet
2- If You use Desktop wallet, keep your private key very secure.
3- Never Keep large amount of bitcoins in online wallet as it is always risky with no control on private key.
Withdraw Bitcoin to Cash1- Use LocalBitcoins site as it is very much trusted site and has a built in escrow system in it for safe trades.
2- Face to face bitcoin transfer with anyone in your area willing to buy bitcoins although its difficult to find one.