1. Double Jump
2. Rail Grind
3. Pull up

To do the double jump you need to jump and then jump a second time as you leave the ground (or just spam spacebar).

Just stick your arm as far as possible over the railing and look down slightly. If you are moving at along the bar when you do this then you keep most of your momentum. (Make sure to hold W.)

Jump up to a ledge and place your hand as far back on the ledge as possible then look down slightly and as your character bobs up, crouch and look down slightly more. (This might take a few attempts to get your character to kinda hang there for a bit) (Make sure to hold W.)

Thank for reading and I hope this helps. Some techniques might take a few attempts so if people need I can try add some videos on how to do it.