Adobe After Effects CS6 upscaled 1440p unable to render in 60 FPS

Good day everyone. I am definitely new here, but have been using AE as well as Premiere Pro for around 3-5 years now, on and off.

I come from a gaming scene where the game with all the flora and background messes up the YT algorithm, which makes the scenes look extremely bad, thus we came up with the idea to upscale the footage to 1440p or even 4K, which helped a lot.

But at that point, we ran into a problem, one, which for whatever reason changed over the years. Whenever we upscaled the footage, we were limited to 30 FPS renders, instead of the 60 FPS we initially selected and worked with. By now, AE still lowers doesn't render with 60 FPS, but with 51.20. This has the problem with it that the music which is attached to it, is all over the place, since it was put in for 60 FPS, while being rendered in 51 FPS. Took me some time to understand that as well. Not fully sure why that is and how to work around that. Would be very glad for some help. How does this happen and how could I fix this? I am currently working on a new project and would love to be able to render it in 60 FPS, however as of right now, this is impossible.

Additional infos: I tried around in Premiere today, in order to render it in there, in 1440p, but it wouldn't let me since there is no pre-setting for 1440p in CS6. Trying to put it together myself, it limits it to 30 FPS instead of 60.

I put some screenshots in as well so you can see the actual numbers and render/composition settings. My apologies for it being in german. The example is in 4K, however represents the 1440p situation perfectly as well.

Thanks for answers in advance.

Alpha