Another vote for assertiveness training here. You have past issues, and I think your online name has some clues. You say you panic when people explain things to you. Why is that? I would have a little reporter's notebook and pen handy at all times, and when the manager approaches you, just say: "I'll just make a few notes as an aide memoire." That gives you a little breathing space, and you will be looking at your notebook and not at him as you write. Put the date and time and write down brief notes of what he says. Write verbatim anything threatening or inappropriate. This will also have the effect of putting him on notice without you having to be too obvious you are onto him. You can say: "Okay, I'll take a look at that," and then do just that. Has he suggested something useful, albeit in an unfortunate manner? If so, you can do as he suggested. If it's all or mostly negative, the pattern will be clear and you have the notes to take to a senior manager or HR. We all come across bullies at work; I have certainly suffered a fair few. You need to develop tactics and strategies to deal with them. Good luck!
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