Advice on 500mm mk1 or 600mm mk1

[derrt]

I am currently looking to purchase a big prime for a improvement in image quality and lowlight performance. Currently I shoot with the R7 and the RF200-800mm, however I am debating also upgrading my body to an R5 or R6 mk2 also due to some issues with my R7. I know that the mark one lenses are not necessarily ideal however for the price point and where I am at in my photography skills they are what I am looking for. Any advice or input to help me decide between the two lenses or the bodies. For some context I shoot wildlife(anything furry small or big) and some birds mainly owls, I am located in Wyoming so there is a large variety of shooting distances out in the sage or in the timber. I am also looking into using blinds (+ tripod) more so that way I could help offset some of the “negatives” of the old primes. I also have never owned a prime lens so I would need to get used to the inflexibility of the prime vs the zoom. I plan to keep both my R7 and 200-800 as backups, and weight is not to much of an issue I’m young and dumb with a strong back.

[shadowsports]

Greetings

Some questions for you. 

What isn't the R7 and RF200-800 not doing for you now?

What issues are you having with your R7? Does it need service? 

Do you have a budget for your potential upgrades?

The AF and light gathering performance of the R6mkII is formidable.  The R5 will offer higher resolution and the potential for more cropping of images.  

Budget and these performance options might influence a purchase decision.