Make sure to back up important emails/messages that can be used as supporting evidence. If using Outlook, you can download all emails in a .PST file, sometimes a .OST file, if you send emails for your job.

Save them onto a flash drive, that way if they lock you out of everything before you come in one day, you have all that saved still and they cannot deny it later.

If you live in a place that allows 1 party consent recording, you can use your phone or other hidden device to record any important conversations.

I would also back up copies of any employee documents. Employee handbooks, company rules, hiring agreements, NDAs, Non-competes, memos, etc. Corrupt companies and bosses have been known to lie about former company agreements and modify documents to attempt to discredit former employees, so it's important to have copies of these documents on your own flash drive or phone just in case.

Keeping a daily log also can help refute claims that you aren't performing your duties properly or are coming in late/leaving early.

Good luck and stay strong!

Probably helpful to find an attorney who specializes in these cases. If they have free consultations you can talk to them and get much better advice and help, plus be able to talk to them immediately if you do get retaliated against or even feel like something may fall under retaliation