Sometime every 2-5sec buffer size decreased more than 1 sec

Hello! Sorry for digging this topic.
Didn’t want to create new topic but i have problem with the small buffer size. Wish there would be a way to force so buffer wont be empty.
F.ex. watching: Twitch

stream stats -Imgur: The magic of the Internet
I know my internet is not all that good but still think its enough to watch stream.