long render times

Hi,
i edited a 2 minute music video. 4K Raw, Grading, neat video denoise, glow... etc on the color page. Dissolve blends on the edit page. It plays perfectly in ram preview. Now I want to render ist out as HD1080 H264 - and it takes an hour!
It seems the most problems it has on the dissolving parts... whre clips are blended together in the timeline.
Why?
i edited a 2 minute music video. 4K Raw, Grading, neat video denoise, glow... etc on the color page. Dissolve blends on the edit page. It plays perfectly in ram preview. Now I want to render ist out as HD1080 H264 - and it takes an hour!
It seems the most problems it has on the dissolving parts... whre clips are blended together in the timeline.
Why?