OS Catalina H.265 files and VLC

[rvb1960]

First, sorry for my bad English.
I bought a new Mac for making video's.
I still have some 4K movies MP4 in H.265 code.

They play well on Quick Time Player and on VLC player.
But when I want to import the file in any video making program it sucks. The movie gets grey/faded.

So I try to convert the file from H.265 to H.264. H.264 must work fine in any video adding program.

My file plays well in VLC. It bit less grey but its ok !!
But..........when I convert it to H.264 MP4 it gets grey/fading again. How?? I try all export files but it all gets faded.

What do I do wrong?
1st picture is playing in VLC
2nd picture is the result after converting to MP4 H.264.

https://imgur.com/a/wPVrjvv