What solution to use in order to fix a block in another block?

Question

css

There is such a task, to fix the block, so that when it scrolls to it, it becomes fixed
AND rides within the framework of another block, while reaching a certain point (conditionally the basement) it sticks to it
After which we scroll up it again comes off
The fact is that in the basement there can be a different number of elements
I already tried to count relative to the window, relative to the block in which it travels
But something breaks all the time
Are there any solutions or plugins ^ Maybe someone has already done this
Thank you

Answer 1

position: sticky
But low browser support so use
wd.dizaina.net/en/scripts/stickyfill