Sick Tricks

Here are some things that helped me:

-In settings, change the skip cutscene and gui menu settings to the fastest. To skip a cutscene, click esc and z.

-Use the fast route, where you have to clip through the ground in the beginning. You have to face the wall ~45 degrees to the left in order to clip through. This is also the route speedrunners use

-After taking the taxi ride, jump on top of it via its door then jump onto the platform behind where the purple cockroach guy runs away from you, this skips the building cutscene so you can now jump back down and walk towards the path ahead of the taxi to enter the ear.

--MAIN PART--

-If you click alt+f4 very quickly just as you fall in the river, you can start the parkour again. I reassigned one of my keys to make this faster.
-For me, i clicked all sprint settings to off so i had to hold down shift to sprint. This prevented confusion as to whether i was in sprint mode or not.
-Some people say you only sprint jump the fourth jump, but for me I kept falling down and couldn't even reach the second platform. I had to sprint jump every single one of them instead and use my mouse to slightly correct the landings.
-Do not use A or D to correct your jump, but use the mouse to correct it instead.
-You can click esc to enter the pause menu while standing on one of the platforms to see which hallucination is the correct one and predict its movements
-Use the red stripes on the platforms to estimate an alignment with your platform and jump when you feel right.

-BE PATIENT

links

Skip to 0:35 for clipping under the ground
Skip to 2:40 for the taxi part

[OrangeKRUSH]

using the head nulls the achievement, sadly. supposedly jumping on the second row of platforms from the bridge nulls the achievement too

[shittin in the grass]

why not just use the head to get across the bridge?