It is impossible to say. If you are that concerned you should use something else

I personally wouldn't touch WhatsApp with a 10foot pole. As it is owned by Facebook, the company who earlier this year paid a company to compromise TAILS OS to find a pedo. Which its not the fact that they threw a pedo in jail. But the fact they compromised anonymity and in no way are a government body!!! So glowies be glowing hard at Facebook.

They also have done other spooky shit. Which is why the only reason I use Facebook is to sell my shit.

We could also talk about the OS and hardware your using to message people for security. If you want to know more read permanent record by Edward snowden. Its a great book and talks alot about PRISM and other spooky stuff

It does not matter how good the encryption is. The app on your device has to be able to decrypt the content to be able to show it to you. If it has access to the decrypted data, it could just send it somewhere. If it has access to your private key, it can leak it. Even if the app is open source, you do not know if the binary on your phone matches that source, unless it uses reproducible builds and you actually verify the binary on your particular device, after each update.

Ask Meta. Its not Open source, its all "trust me bro its encrypted with some encryption"

Governments, if they want, can decrypt any chat, not just Whatscrap. But it makes a difference if a chat, especially this Zuckerbot shit, directly opens a Backdoor to governments, to give them access, or if they have to bother hacking the chats themselves, which due to its cost and time, is only done with a court order.