Have Internet connection problems constantly, what to do?

Hello for a few days a new Internet connection. Only the problem is that I can hardly use the Internet because the WLAN comes to a standstill after a few minutes. Here's an example: turn on the phone on a Youtube video and it works in half then it hangs because it runs faster than the loading bar of the video. Then it shows me the WLAN with an exclamation mark on the smartphone. After that, nothing is more and it switches to mobile data. The laptop is the same game. It shows me connected but at the same time if I want to open a page "no internet". What can I do there? And the router lights up normally. Have already reset and taken everything from the power.

I had that with the Telekom too - I called there, which changed something since everything runs perfectly

Either the Internet connection is disturbed or the WLAN.

Both you have to be able to monitor the router, s.besten times with a LAN cable connect and look…

Do you still know what you have changed because then I can say that tomorrow Vodafone times

No!

As absolute technology rivets I have it understood that because of the transmission… Frequency? What was changed

BUT WITHOUT ANY WARRANTY