DaVinci lagging so much with .PNG graphics

Hi,

I made simple dance video with just 2 cuts (3 clips).
Recorded with BMPCC 6k with 6k BRAW format.

I added little watermark graphic in the corner of video in .PNG format and after stretching this graphic on whole video (1:30 min) all the playback and render slowed down like 900%. I can't playback because it's 0-0.5 FPS. Render slowed down from 0:56 sec to 3 hours (JUST FROM ADDING SOME PNG GRAPHIC!).

iMac Big Sur 11.2.3
Retina 5k, 27-inch, Late 2014
4 Ghz Quad-Core Intel Core i7
RAM 16 GB 1600 Mhz DDR3
AMD Radeon R9 M290X 2GB

I know all the tips about making DaVinci working fast, so it's not the case.

Why PNG graphic slows down everything so much?

Thank you very much in advance!
Best Regards

[Peter Chamberlain]

What is the resolution of the graphic?

Ohhh just checked.

12548x12548

That's the case. I didn't bother with it because I saw that the file was only 900kb, but still resolution plays key role here.

Thank you!