Problems streaming to mixer what to do?

Yesterday I streamed on mixer for the first time with the game gta 5.

When I drove through the city quite relaxed, the city hardly loaded.

I didn't have that when I was streaming on Twitch.

(My hardware: i5 4-core 3.2, 16 GB RAM, with the graphics card I'm not sure whether radeon rx 570 8gb or 580 8gb.

With a 4 core, it won't work

You can either raise the priority for gta5, which will likely result in the stream being lagged, or you can stream via the GPU, which should be fast enough

How can I change that?

The i5 is just too weak for that. You can only try to encode via the GPU.

Where and how could I try / do it?

In your stream program.