Can I block the time between reservations for resource refuel/cleaning etc.?

Yes.
In the resource settings, select the Block time between reservations checkbox and specify the desired duration.

Yes, you can configure the duration of the blocked time in the resource settings.

For example, if you set this duration to 1 hour, each booking shown on the client's calendar will start 1 hour later and end 1 hour earlier. This ensures that clients cannot book the resource during the designated preparation time (such as refueling or cleaning).
This guarantees a 1-hour gap between bookings.