How do you say only?
How do we pronounce our?
Is it pronounce or Pronunciate?
The correct verb in English is pronounce, not pronunciate. An articulate and well-educated fluent English speaker who used pronunciate as a verb might be assumed to be making a joke.
Is the T silent in exactly?
In practice, yes it is virtually silent unless one makes a special effort to pronounce it. When we have a consonant cluster here /ktl/ one sound is often not heard. The linguistice term for it is “dissimilation”.