I solved the problem with the use of Global Time Dilation and the use of some Custom Time Dilation.
I used some World Delta Seconds in my Camera actors and these variable are modified by the Global Time Dilation, no matter where they are called. So I used the time compensation on them too!
Other tips : Timers are not affected by Custom Time Dilation. And we need to use a minimal value of 0.0001 for Global Time Dilation in order to be able to modify some actors with Custom Time Dilation (because they are multiplicated!).
Thank you for help!