I want to make a new account on math.stackexchange, but I want to import everything from my previous account.
Please do not criticize. Just simply answer the question.
Yes, this is possible. As mentioned in a comment you can ask for two accounts to be merged. All the content (including votes etc.) of one will then be transferred to the other. At the end you'll have one account with the combined data.
To do this follow the instructions given in the Help Center:
More specifically, since it seems you do not yet have this new account, first create your new account and then ask for the old one to be merged into the new one.
That said, if you in fact do not yet have this new account, it might very well be there are better options than this to achieve what you actually want to achieve, but it is hard to tell without further details.