Thank you for your feedback, however you seem to be very vague in mentioning parts of the level you seem to be unable to surf on. Nontheless, I think I have a solution for your problems.

You did mention the double triangle section at the start of the level, however I don't see what the problem could be in this section. You did make sure to dive into the ramp itself directly, yes? It helps if you directly dive into it near the bottom of the slope without jumping first. (Sliding across the ground towards it, however, will not work.)

There is no time limit on how long you can surf on correctly angled ramps, however since Hat Kid is still considered in a "diving" state, pressing the key that is opposite of Hat Kid's direction will cause her to stop wallsurfing, which I assume you may have accidentally done. You can disable this option by going into the pause menu and then Settings -> Input Settings -> Input (Advanced), then toggling "Hold Backwards To Cancel Diving" to off.

If you find any other issues with my mod or see things I missed in this comment, please let me know! I'm always glad to help!