the hot water in my kitchen takes a long time to come out; but in the bathrooms, they come out fast.

Is your kitchen farther from the hot water heater?   If not, measure the water flow from the hot water tap compared to the bathrooms to see if there may be a restriction. 

Call a licensed plumber.  I'm sure they would be able to figure it out rather quickly. 

This is a typical complaint from most homeowners that have a water heater in the garage and the kitchen is at the far side of the home.  There is a solution to this.  There is a retrofit pump and bypass system called a Grundfos Comfort system.  This unit comes with a pump, a bypass valve, and 2 stainless steel hoses.  Here is how it is installed.  You first install the pump on the top of the water heater on the hot/discharge side with the arrow of the pump pointed to the top then plug in the cord to an outlet.  The pump has a dial for which you will need to set the time it is and the time for which you want the valve to circulate.  Whatever your peak hours of water usage is at the sink, set the unit to go off at least 30 minutes before.  Next, you need to get under the kitchen sink and disconnect the single hot and cold tubing to the kitchen faucet.  You will notice that the bypass valve has four ports all 1/2inch iron pipe thread.  Connect the hot 1/2inch tube from the angle stop to the left side of the bypass valve, then connect one of the stainless steel hoses from the bypass valve to the hot side of the kitchen faucet.  Do the same to the cold side.  In the ideal situation, all the old parts connecting to the new parts goes together without creating other problems.  Why did I just do all of this?  Here is the answer:  when the pump is preset to circulate stagnant water, it will move lukewarm water from the hot side towards the cold.  The one negative to this whole thing is that you will get a slight bit of warm water in the cold side after this unit circulates.  Here are the positives:  rather instant hot water at the kitchen, since this loop has hot water the wait time for other fixtures on this line now is shorter, your water bill will be reduce because you are not wasting water while waiting.  Good Luck