How to get better quality on my videos.

Hello.

I am creating videos for TikTok, but recently I faced the problem with quality in my videos.
I am using Adobe Premiere Pro for editing and my render settings are:
format: mp4
fps: 60.
size: 1080 x 1920
VBR, passes: 20, 50 mbps
Use maximum render quality
Render at maximum depth

After this I'm moving mp4 file to my phone and posting with my phone, using as option called: "allow posts in better quality"(because I have already found out that posting with PC cuts quality aswell) using wifi speed 1 gbps.

However, if I am posting videos longer than 10-15 seconds, TikTok cuts the FPS to 25-30 and the resolution of the video too.

I have also seen videos like this: https://www.tiktok.com/@kana.vfx/video/7479255499586784529 , with the quality of the video I could never match.

Maybe you have tips with how could I improve my posts? Maybe it's render settings, maybe the format of the file, I would like to hear about everything that can improve the quality.