OBS Stream is lagging despite a good connection?

I stream on Twitch with Obs and so far there have only been minor connection problems but now I can't stream like that. I only get discarded frames when I click on steam on a game or when I'm just on a website for a short time. This is exactly where the bit rate drops from 4000 to 1000 or 0. Of course, it increases again, but after a few minutes it drops for a few seconds

It can't be due to my PC: I7 6700k, GTX 1080, 64GB Ram, M.2 SSD, water cooling.

I'm recording with OBS at the same time and so far there have only been a few lags in between. I get 10mbps upload but it still lags in the stream. It's not just about Obs, I notice when I'm on a website that it has slowed down. So what can be the reason now?

What kind of internet connection is available? (Down / up / latency)

Despite the good hardware, how is the hardware utilization when playing, recording, streaming?

Is the GPU (hardware) or the CPU (software x264) at the encoding in OBS?

How are the settings: frame rate, bit rate, basic screen, output

How many image sources are there? (static are irrelevant e.g. Alerts)

10Mbit / s is also not necessarily "good"

1080p 30fps alone require ~ 10MBit / s with H264 / 265 / VP9

And if you push your upload with the stream, then other packets, e.g. Transmission may be delayed for a game → high ping
Or the upload becomes so slow (because a request also needs an upload) that the bitrate of the stream breaks down.

I now assume that you mean 4000 kb (4MB), well this internet connection is not good.

How high did you set your video bitrate?