Is it necessary to restart the tasbih from the beginning if it is interrupted before completing the required number, or is what has been recited counted and the remaining number completed?

It is commendable for a Muslim, when remembering Allah the Almighty, to pay attention to that, understand what they are saying, sense the greatness of Allah, and keep track of the count. If some speech intersperses the remembrance, they are not obligated to repeat what has passed; rather, they should complete the count based on that. And if they start counting anew, there is no harm in that, for all of that is remembrance of Allah the Almighty.