Problem with importing quotes

Hi,
I have problem with importing list of quotes on my polish site: https://www.imperiumromanum.edu.pl/

I manually added one quote:

?Kto nie chce umiera?, ten nie chce te? ?y?”

Author: Seneka M?odszy

I export the quote to have the sample format for future importing. Unfortunately I noticed that there is some issue with polish letters. Code looks like that:

[
    {
        "quote": "\"Kto nie chce umiera\u0107, ten nie chce te\u017c \u017cy\u0107\"",
        "author": "<a href=\"http:\/\/www.imperiumromanum.edu.pl\/biografie\/seneka-mlodszy\/\">Seneka M\u0142odszy<\/a>",
        "source": null,
        "tags": null,
        "public": "yes"
    }
]

I was trying to import other quote added to mentioned below code – but I suppose using polish letters is the problem. I got message: “Error in JSON file”.

Can You please suggest me how can I in bulk upload a lot of quotes?

Best regards,
Cosiek

https://www.ads-software.com/plugins/quotes-collection/