Field not updated via Flow

I've created a new object "Sales Support Tickets", in the form it has a lookup with Opportunity.

When the Opportunity is selected, or the form is generated from the Opportunity in question, I would like it to auto populate the Close Date, Stage and Account before the form is saved.

I've managed to get it so that when the opportunity the Sales Support Ticket is associated with is changed, the fields update via a Flow however, I cannot get it to do it prior to the form being saved or even after the form has been saved. The opportunity must be changed for it to work.

I cannot work out what conditions I need to set.

I've experimented with a few different options but I end up with the same result.

Any help/insight that anyone can provide would be greatly appreciated.