I was wondering if Instagram could be hacked and get phone number, chats, mail

Yes. This is stored unencrypted (except if you manually enabled end to end encryption for every chat)

maybe the password of an account

Yes, but usually no. Passwords are stored hashed in the database, so if you chose a good password and someone stole the database, bruteforce/guessing your password won‘t be successful. What in theory could also happen is that someone would take complete control over instagrams infrastructure and just log your passwords when it‘s transmitted, before it‘s hashed, but this is EXTREMELY unlikely to happen, not only to happen in the first place but to also be unnoticed. I may notice that this is only a theoretical problem, because you should choose unique passwords for every account anyway.

Same with WhatsApp I, can someone hack it and get the chat?

No. WhatsApp Chats are end to end encrypted. Only you and the person you chat with can read the messages. However, WhatsApp collects a lot of metadata (such as who you text with, when and where, etc.), so that in theory could leak. Also, if you store your WhatsApp backups in the cloud, you need to enable the encryption for it in the settings, because otherwise all your chats are readable by the cloud provider (such as apple or google).

Don‘t be paranoid, but be careful. If you don‘t use one already, go install a password manager and change your passwords with it. Always read privacy policies and check whether the thing you’re using is actually private (for example, you should rather use WhatsApp instead of Instagram chats. As a side note, you should also use something like Signal instead of WhatsApp, but this is not always doable). Again, that meta would actually be hacked this bad is very, very unlikely, but still keep in mind that might no criminal is going to misuse your private information, but the company you‘re sharing your data with might is.