I saved a copy of my wallet.dat as a backup, i used it to transfer 1 btc to another address, now it's got 1 btc less in the total. now I deleted the wallet.dat and open the wallet with the saved wallet.dat before the transaction, I can see a higher balance(it not showing 1 btc off). how could it be? do I lost my whole balance from not saving the newest wallet.dat?
The important thing you should clarify is if the address to which you transfer your BTC belongs to the same wallet or another one.
A wallet is just a collection of addresses which have been created by the same Private Key/Seed. In case you created a new address from the same key (belonging in the same wallet) then You should see the BTC you sent in your balance (minus the transaction fee).
It is also possible that your transaction has not been processed yet.
Without additional information we are unable to help.