I have some positive experience with using this book [1] to older students, I hope you can use your smartphone to translate it from Russian. The book is very much about sets which are shown as bags. It is supposed exactly for math geniuses as I can judge. I do not think showing this book from the screen is a good idea not only because it is on foreign for you language but also because it requires student to write down in it. But you can print a few translated by you pages or maybe recreate the illustrations with a real-world examples (bricks with letters, toys of defined parameters such as color, shape, type of entity etc, arranged in clearly visible groups).

Also if you play music try to return to the very roots of our civilization and explain Math like Pythagoras did - using consonance/dissonance of two strings with defined relative thickness/length.

And please do not introduce him to smartphones! If the parents did that (which is highly likely nowadays) at least do not show the kid that you have it somewhere in your house or your effort will be wasted!

[1] https://file.11klasov.net/1733-matematika-1-klass-uchebnik-c...

PS. The first task requires you to see what are rows, what are columns and a way of visualizing 12345, I tell you this because it was hard to me when I first time opened the book.