Internet does not work with videos?

I have the following problem. I have noticed that my WLAN seems to be too weak for videos?! I can do everything as before, so go to apps, like photos, play games, and also netflix works. The only thing that does not work is watch videos, whether on YouTube, insta or if it is advertising. All that comes is a black picture or it loads all the time.

Does anyone have any idea what's going on?

1) View tariff and see if you have a contracted transfer rate that still applies

2) Check the transmission rate of your connection, eg. B. With https://www.wieistmeineip.de/speedtest/ or similar

3) If there's a discrepancy: contact the provider and ask for a solution