Issues when inserting P6 Programme

Hello house,

I will appreciate any help on the issue I am currently facing:

I copied a subcontractor Xer File to my Master Schedule . This plan was moved to a WBS within the master schedule, however I am now facing an issue where  a number of activities adopted a global calendar therefore their dates are all over the place

Is there a way I could this or I'll need to go back to the inserted programme and change the calendar manually ?

Secondly, when I aligned the calendar and schedule the programme, I notice the inserted programme now in a WBS of the master schedule is generating a negative float despite maintaning the same DD to the last secs.

Any guidance on the above 2 issues will be highly appreciated