Ive been thinking that if your are holding big amount of bitcoin and you want it to transfer to fiat where i can withdraw it without any problem
Here you have many options to convert into cash , First option is to have account at coinbas ( since It is a long term running third party Wallet ) coinbase Wallet has many options of handle your bitcoin with another coin also , so you can use coinbase .
Second opinion that is made for fiat in INR ( India where I am ) is zebpay , most trusted and without any problem .
Third option is to get a bitcoin trader in your local area , you can easily find ( make Google search , hopefully you can found nearby to you.
Fourth option is to get at localbitcoins.com where you can found directly buyers and sellers for every possible type of payment option .