I'm tasked with making this query run under 4 seconds
The optimizer has pointed out there is a potential missing index on Object2 (right click on the SELECT in the plan and choose the Missing Index Details… option).
Object5.Index5 is being read twice, with the same row count for both on the read, then the same sort is being done. I recommend investigating methods to only do the work on Object5 one time. This may include using a temp table and/or rewriting the query and joins.
There is also a Table Valued Function being used on Object8, I would investigate removing the use of the TVF. It is the highest CPU cost in your plan.
Providing more details of the query and options you have tried can provide a better view and allow us to provide more detailed help.