Do you know if there is any food in the fridge? This house is very big. It'll take about twenty minutes to go around of it. How many people can fit on the the bus? What is the maximum passenger capacity of the bus? How do you spend your free time?

It isn't correct to say '..to go around OF it". "To go around it" is correct.

1)Do you know whether there is any food in the fridge(or not) = Do you know if there is any food in the fridge (or not) We can use if or whether to answer indirect yes-no questions . If is more common than whether .In this context , there are interchangeable. 2) This house is very big , and it'll take about twenty minutes to go around of it. This house is very big ; it'll take about twenty minutes to go around of it. This house is very big . It'll take about twenty minutes to go around of it. This house is so big that it'll take about twenty minutes to go around of it. 3)How many people can the bus take? > meaning "how many people are allowed to take the bus) How many people can the bus take ? Meaning "How many people the bus can have as passengers? ( might be to maximun capacity or not --depending on the conversational context ) 4)On what (hobby)do you devote your free time? > Not sure about this , sounds ok to me. >I spend a lot of free time on what I like to do ,such as reading What do you do during your free time?