I have tried millions of times to reach to the top of the building and I can't make it happen. Have I missed something? Thanks in advance.

To get an optimal glitched high jump you must spin as soon after the jump as possible. If you spin the frame after jumping, you will get the highest jump possible.

You can get more height in the double jump if you spin though it is not necessary for the hangrail skip.

Note that while doing runs you should only attempt the hangrail skip once. If you fail to get up there the first time, just proceed normally. It's not worth it to keep attempting it.

Also, feel free to join the Crash Speedrunning Discord server, where you can ask questions and be more likely to receive help faster from others.

https://discord.com/invite/d3y5jHj