Possible to play FM in windowed mode, while streaming?

[oyz]

I have a question about multitasking when playing FM21. 

I have an ultrawide monitor and prefer playing FM21 in windowed mode. That gives me a part of the screen where I would like to have other stuff going on. For example, I would like to be able to stream football games there simultaneous with playing FM21.

That doesn't work in practice. Doing other things while FM21 is on, makes both FM and whatever else I'm doing to lag and stutter. Sometimes it can work decently for a while for some reason, but even in those cases it stops when a game is on in FM21. Then things comes to a halt, and both the video stream and the FM-graphics is more or less unworkable because of lagging.

Is this a computer-problem, a settings-problem or just an unexplainable problem.
Or is it just how it is, because of the limitations of technology?

I am not really into the techniichal sides of computers, so I don't really know what to expect or where to begin,

I am playing with a
Dell XPS 15 9570, i7-8750H CPU @ 2,2 Ghz
32 GB Ram
NVIDIA Gforce GTX 1050 Ti
Connected to high speed broadband by wire.