Obtaining a Luxury Item (Assassin's Creed: Rogue)

Hello everyone. Faced the problem of obtaining a luxury item in Valais Werth, coordinates 972, -581. Such a yellow diamond. Located at the top of the tree. I just can't get it. You can't jump, I run alongside - I can't. Help - how to get it.
And the second question - if during a robbery of a warehouse (when you first need to find the key keeper and then rob the warehouse) the key keeper managed to escape and the warehouse became confused, then can you somehow replay this moment? After quite a long time, the warehouse does not open for repeated passage.

[UPD] with the first question - a solution has been found.