Why is streaming so slow?

First of all: I have a 2018 Huawei p smart.

Now to the problem:

My internet speed via Wi-Fi on my cell phone is very bad with streaming. That means YouTube doesn't run at 144p, you can also forget Spotify.

The funny thing is that everything else works well and quickly, i.e. Both other functions and streaming on other devices. Everything works great with mobile data. What can that be?

Internet is sometimes critical At the moment everyone is at home

Hmm, yes, but there's actually enough. Just did a speed test, 4mbps is not much, but should be enough.

For yt this is not always enough, especially with long videos

I have already reduced my claim to 360p.

Yes that can still go on the internet

Did you do the speed test on your cell phone? It is probably due to the Wi-Fi. Stand with the cell phone right next to the router and test again.