Hello Bitcoin community,

I am totally new to Bitcoin and at the moment i am a bit shocked.

Recently I downloaded the Bitcoin Core wallet onto my Macbook and installed/synchronized all.
Received some coins in that wallet and closed it.

Opened the wallet next day again, and.... it's gone. no more BTC, no more transaction, no more address, all empty.
The wallet.dat file is still present but the wallet doesn't read the content of the wallet.dat file as it looks like.

I want my BTC to show up again.

Does anybody know how to put back a wallet.dat file in a Bitcoin Core wallet on a Macbook?

In my desktop there is now two files: wallet.dat and Wallet copy.dat?

How do I get this wallet to work again?

Help!!